DnaA

Last updated
Chromosomal replication initiator protein dnaA
Identifiers
Organism Escherichia coli
(str. K-12 substr. MG1655)
SymbolDnaA
Entrez 948217
RefSeq (Prot) NP_418157.1
UniProt P03004
Other data
Chromosome genome: 3.88 - 3.88 Mb
Search for
Structures Swiss-model
Domains InterPro
Bac_DnaA_C
PDB 1j1v EBI.jpg
crystal structure of dnaa domainiv complexed with dnaabox dna
Identifiers
SymbolBac_DnaA_C
Pfam PF08299
Pfam clan CL0123
InterPro IPR013159
SCOP2 1j1v / SCOPe / SUPFAM
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary

DnaA is a protein that activates initiation of DNA replication in bacteria. [1] Based on the Replicon Model, a positively active initiator molecule contacts with a particular spot on a circular chromosome called the replicator to start DNA replication. [2] It is a replication initiation factor which promotes the unwinding of DNA at oriC. [1] The DnaA proteins found in all bacteria engage with the DnaA boxes to start chromosomal replication. In addition to the DnaA protein, its concentration, binding to DnaA-boxes, and binding of ATP or ADP, we will cover the regulation of the DnaA gene, the unique characteristics of the DnaA gene expression, promoter strength, and translation efficiency. [2] The onset of the initiation phase of DNA replication is determined by the concentration of DnaA. [1] DnaA accumulates during growth and then triggers the initiation of replication. [1] Replication begins with active DnaA binding to 9-mer (9-bp) repeats upstream of oriC. [1] Binding of DnaA leads to strand separation at the 13-mer repeats. [1] This binding causes the DNA to loop in preparation for melting open by the helicase DnaB. [1]

Contents

Bac_DnaA
PDB 2hcb EBI.jpg
structure of amppcp-bound dnaa from aquifex aeolicus
Identifiers
SymbolBac_DnaA
Pfam PF00308
Pfam clan CL0023
InterPro IPR013317
PROSITE PDOC00771
SCOP2 1j1v / SCOPe / SUPFAM
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary

Function

DnaA consists mainly in two different forms, the active ATP-form and the inactive ADP. [1] [3] The level of active DnaA within a cell is low immediately after a cell has divided. [1] Although the active form of DnaA requires ATP, the formation of the oriC/DnaA complex and subsequent DNA unwinding does not require ATP hydrolysis. [4]

The oriC site in E. coli has three A T rich 13 base pair regions (DUEs) followed by four 9 bp regions with the sequence TTAT(C or A)CA(C or A)A. [5] Around 10 DnaA molecules bind to the 9 bp regions, which wrap around the proteins causing the DNA at the AT-rich region to unwind. There are 8 DnaA binding sites within oriC, to which DnaA binds with differential affinity. When DNA replication is about to commence, DnaA occupies all of the high and low affinity binding sites. The denatured AT-rich region allows for the recruitment of DnaB (helicase), which complexes with DnaC (helicase loader). DnaC helps the helicase to bind to and to properly accommodate the ssDNA at the 13 bp region; this is accomplished by ATP hydrolysis, after which DnaC is released. Single-strand binding proteins (SSBs) stabilize the single DNA strands in order to maintain the replication bubble. DnaB is a 5'→3' helicase, so it travels on the lagging strand. It associates with DnaG (a primase) to form the only primer for the leading strand and to add RNA primers on the lagging strand. The interaction between DnaG and DnaB is necessary to control the longitude of Okazaki fragments on the lagging strand. DNA polymerase III is then able to start DNA replication.

DnaA is made up of four domains: the first is the N-terminal that associates with regulatory proteins, the second is a helical linker region, the third domain is a AAA+ region that binds to ATP, and the fourth domain is the C-terminal DNA binding region. [6] DnaA contains two conserved regions: the first is located in the central part of the protein and corresponds to the ATP-binding domain, the second is located in the C-terminal half and is involved in DNA-binding. [7]

DnaA mutants

The first strains to have the dnaA gene mutated were the temperature-sensitive K-12 strains CRT46 and CRT83, with the corresponding strain numbers beingdnaA46 and dnaA83. In contrary to dnaA mutants, the PC2 strain has a mutation in the dnaC gene, which codes for the loading factor for the DNA helicase dnaB. [8]

Synthesis

DnaA has the ability to bind its own promoter. When DnaA binds to its own promoter it blocks RNA polymerase from binding the promoter and inhibits initiation of transcription. In this way, DnaA is able to regulate its own expression. [3] [9] This process is called autoregulation. [10]

Regulation

Each cell division cycle triggers a new round of chromosome replication by DnaA, the initiator protein. It is crucial to regulate DnaA-ATP monomer interactions with oriC during helicase loading and unwinding of origin DNA for precise timing. DnaA recognition sites in Escherichia coli are arranged in OriC to facilitate staged pre-replication complex assembling, with DnaA interacting with low affinity sites at it oligomerizes to fill the gaps between high affinity sites as it oligomerizes. There may be numerous gap-filling strategies to link OriC functions to bacterial lifestyles in nature, which may account for the wide variability of OriC DnaA recognition site patterns. [11] The two forms of DnaA, the active ATP- and ADP-form are regulated. The ATP-form is converted to the ADP-form through either Regulatory inactivation of DnaA (RIDA), [12] which in turn consists of the Hda protein and the β sliding clamp (DnaN) [13] and datA-dependent DnaA-ATP hydrolysis. [14] The ADP-form is converted to the ATP-form by DnaA-reactivating sequences 1 and 2 (DARS1 and DARS2). [15]

DnaA protein structure

There are four disciplines within the DnaA protein. An initial comparison of Escherichia coli and Bacillus subtilis proteins led to the discovery of a sphere structure, which revealed a relatively conserved N-terminus and a largely conserved large C-terminus separated by a region that was mostly variable. [16] As an example, the Enterobacterial proteins have nearly identical N- and C-terminal sequences, however they are characterized by numerous amino acid adjustments, elisions, and insertions in the variable regions. [17] There is an AAA+ family ATPase motif and an independent DNA binding sphere in the C-terminal region. It was determined by NMR that Escherichia coli sphere IV had a crystal-clear structure when complexed with a DnaA- box. As a result, it was confirmed that the DNA list is intermediated by a combination of a helix-turn-helix motif and an introductory circle. When bound to ATP, but not to ADP, DnaA forms a super-helical structure with four monomers per turn. The structure of sphere I has been determined from three additional bacterial species and Escherichia coli by NMR. [18]

Autoregulation of DnaA protein synthesis

DnaA protein structure PDB 1pji EBI.jpg
DnaA protein structure

The research on dnaA(Ts) mutants provided the first proof that the dnaA gene is autoregulated. DnaA protein is still produced at non-permissive temperatures where it is inactive, but in some mutants it can be made active again by returning to a temperature that is conducive to development. [17] This reversible initiation capacity—which was larger than anticipated given the mass gain of the culture—could be seen in the absence of protein synthesis at the permissive temperature and suggested that the DnaA protein synthesis was derepressed at the high growth temperature. These results prompted a thorough investigation of the dnaA46 mutant under permissive, intermediate, and non-permissive development conditions. [19] The study's findings revealed that as growth temperature increased, the DnaA46 protein's activity decreased, leading to progressively decreasing DNA and origin concentrations at intermediate temperatures. An increase in initiation capacity was seen concurrently with a decrease in DnaA protein activity. Hansen and Rasmussen (1977) argued that the DnaA protein had a positive effect in replication initiation aing transcripts entering the dnaA gene were found as a result of sequencing the dnaA promoter region and the dnaA gene. [19] The DnaA promoter region has nine GATC sites within 225 base pairs, and a sequence that is similar to nd a negative role in its own synthesis based on these observations. Two promoters providrepetitions (DnaA-boxes) in the oriC region was found between the two promoters. According to several studies, the DnaA protein negatively regulates both promoters. In these research, it was discovered that the dnaA transcription was upregulated by 4- to 5-fold at non-permissive temperatures in dnaATs mutants and repressed by the same amount when DnaA protein was overproduced. The autoregulation of the dnaA gene requires the DnaA-box. [20] The sequence of the dnaA2p promoter region has some intriguing characteristics that can be seen more clearly. This promoter contains two GATC sites, one in the 10 sequence and the other in the 35 sequence, and both in vivo and in vitro, methylation increases transcription from this promoter by a factor of two. In addition, DnaA protein binds to regions upstream of the dnaA2p promoter with a high affinity. [10]

See also

Related Research Articles

<span class="mw-page-title-main">DNA replication</span> Biological process

In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part of biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential.

<span class="mw-page-title-main">Lambda phage</span> Bacteriophage that infects Escherichia coli

Enterobacteria phage λ is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli. It was discovered by Esther Lederberg in 1950. The wild type of this virus has a temperate life cycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase, during which it kills and lyses the cell to produce offspring. Lambda strains, mutated at specific sites, are unable to lysogenize cells; instead, they grow and enter the lytic cycle after superinfecting an already lysogenized cell.

dnaB helicase

DnaB helicase is an enzyme in bacteria which opens the replication fork during DNA replication. Although the mechanism by which DnaB both couples ATP hydrolysis to translocation along DNA and denatures the duplex is unknown, a change in the quaternary structure of the protein involving dimerisation of the N-terminal domain has been observed and may occur during the enzymatic cycle. Initially when DnaB binds to dnaA, it is associated with dnaC, a negative regulator. After DnaC dissociates, DnaB binds dnaG.

<span class="mw-page-title-main">Origin of replication</span> Sequence in a genome

The origin of replication is a particular sequence in a genome at which replication is initiated. Propagation of the genetic material between generations requires timely and accurate duplication of DNA by semiconservative replication prior to cell division to ensure each daughter cell receives the full complement of chromosomes. This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses. Synthesis of daughter strands starts at discrete sites, termed replication origins, and proceeds in a bidirectional manner until all genomic DNA is replicated. Despite the fundamental nature of these events, organisms have evolved surprisingly divergent strategies that control replication onset. Although the specific replication origin organization structure and recognition varies from species to species, some common characteristics are shared.

<span class="mw-page-title-main">Pre-replication complex</span>

A pre-replication complex (pre-RC) is a protein complex that forms at the origin of replication during the initiation step of DNA replication. Formation of the pre-RC is required for DNA replication to occur. Complete and faithful replication of the genome ensures that each daughter cell will carry the same genetic information as the parent cell. Accordingly, formation of the pre-RC is a very important part of the cell cycle.

<span class="mw-page-title-main">Nucleoid</span> Region within a prokaryotic cell containing genetic material

The nucleoid is an irregularly shaped region within the prokaryotic cell that contains all or most of the genetic material. The chromosome of a typical prokaryote is circular, and its length is very large compared to the cell dimensions, so it needs to be compacted in order to fit. In contrast to the nucleus of a eukaryotic cell, it is not surrounded by a nuclear membrane. Instead, the nucleoid forms by condensation and functional arrangement with the help of chromosomal architectural proteins and RNA molecules as well as DNA supercoiling. The length of a genome widely varies and a cell may contain multiple copies of it.

<span class="mw-page-title-main">DNA unwinding element</span> Initiation site for the opening of the DNA double helix

A DNA unwinding element is the initiation site for the opening of the double helix structure of the DNA at the origin of replication for DNA synthesis. It is A-T rich and denatures easily due to its low helical stability, which allows the single-strand region to be recognized by origin recognition complex.

<span class="mw-page-title-main">DNA adenine methylase</span> Prokaryotic enzyme

DNA adenine methylase, (Dam methylase) (also site-specific DNA-methyltransferase (adenine-specific), EC 2.1.1.72, modification methylase, restriction-modification system) is an enzyme that adds a methyl group to the adenine of the sequence 5'-GATC-3' in newly synthesized DNA. Immediately after DNA synthesis, the daughter strand remains unmethylated for a short time. It is an orphan methyltransferase that is not part of a restriction-modification system and regulates gene expression. This enzyme catalyses the following chemical reaction

<span class="mw-page-title-main">Prokaryotic DNA replication</span> DNA Replication in prokaryotes

Prokaryotic DNA Replication is the process by which a prokaryote duplicates its DNA into another copy that is passed on to daughter cells. Although it is often studied in the model organism E. coli, other bacteria show many similarities. Replication is bi-directional and originates at a single origin of replication (OriC). It consists of three steps: Initiation, elongation, and termination.

fis E. coli gene

fis is an E. coli gene encoding the Fis protein. The regulation of this gene is more complex than most other genes in the E. coli genome, as Fis is an important protein which regulates expression of other genes. It is supposed that fis is regulated by H-NS, IHF and CRP. It also regulates its own expression (autoregulation). Fis is one of the most abundant DNA binding proteins in Escherichia coli under nutrient-rich growth conditions.

<span class="mw-page-title-main">Guanosine pentaphosphate</span> Chemical compound

(p)ppGpp, guanosine pentaphosphate and tetraphosphate, also known as the "magic spot" nucleotides, are alarmones involved in the stringent response in bacteria that cause the inhibition of RNA synthesis when there is a shortage of amino acids. This inhibition by (p)ppGpp decreases translation in the cell, conserving amino acids present. Furthermore, ppGpp and pppGpp cause the up-regulation of many other genes involved in stress response such as the genes for amino acid uptake and biosynthesis.

<span class="mw-page-title-main">T7 DNA polymerase</span>

T7 DNA polymerase is an enzyme used during the DNA replication of the T7 bacteriophage. During this process, the DNA polymerase “reads” existing DNA strands and creates two new strands that match the existing ones. The T7 DNA polymerase requires a host factor, E. coli thioredoxin, in order to carry out its function. This helps stabilize the binding of the necessary protein to the primer-template to improve processivity by more than 100-fold, which is a feature unique to this enzyme. It is a member of the Family A DNA polymerases, which include E. coli DNA polymerase I and Taq DNA polymerase.

<span class="mw-page-title-main">Replication terminator Tus family</span>

Tus, also known as terminus utilization substance, is a protein that binds to terminator sequences and acts as a counter-helicase when it comes in contact with an advancing helicase. The bound Tus protein effectively halts DNA polymerase movement. Tus helps end DNA replication in prokaryotes.

<span class="mw-page-title-main">Circular chromosome</span> Type of chromosome

A circular chromosome is a chromosome in bacteria, archaea, mitochondria, and chloroplasts, in the form of a molecule of circular DNA, unlike the linear chromosome of most eukaryotes.

<span class="mw-page-title-main">Bacteriophage P2</span> Species of virus

Bacteriophage P2, scientific name Escherichia virus P2, is a temperate phage that infects E. coli. It is a tailed virus with a contractile sheath and is thus classified in the genus Peduovirus, subfamily Peduovirinae, family Myoviridae within order Caudovirales. This genus of viruses includes many P2-like phages as well as the satellite phage P4.

<span class="mw-page-title-main">SeqA protein</span>

In molecular biology the SeqA protein is found in bacteria and archaea. The function of this protein is highly important in DNA replication. The protein negatively regulates the initiation of DNA replication at the origin of replication, in Escherichia coli, OriC. Additionally the protein plays a further role in sequestration. The importance of this protein is vital, without its help in DNA replication, cell division and other crucial processes could not occur. This protein domain is thought to be part of a much larger protein complex which includes other proteins such as SeqB.

<span class="mw-page-title-main">Bacterial DNA binding protein</span>

In molecular biology, bacterial DNA binding proteins are a family of small, usually basic proteins of about 90 residues that bind DNA and are known as histone-like proteins. Since bacterial binding proteins have a diversity of functions, it has been difficult to develop a common function for all of them. They are commonly referred to as histone-like and have many similar traits with the eukaryotic histone proteins. Eukaryotic histones package DNA to help it to fit in the nucleus, and they are known to be the most conserved proteins in nature. Examples include the HU protein in Escherichia coli, a dimer of closely related alpha and beta chains and in other bacteria can be a dimer of identical chains. HU-type proteins have been found in a variety of bacteria and archaea, and are also encoded in the chloroplast genome of some algae. The integration host factor (IHF), a dimer of closely related chains which is suggested to function in genetic recombination as well as in translational and transcriptional control is found in Enterobacteria and viral proteins including the African swine fever virus protein A104R.

The gua operon is responsible for regulating the synthesis of guanosine mono phosphate (GMP), a purine nucleotide, from inosine monophosphate. It consists of two structural genes guaB (encodes for IMP dehydrogenase or and guaA apart from the promoter and operator region.

DNA Polymerase V is a polymerase enzyme involved in DNA repair mechanisms in bacteria, such as Escherichia coli. It is composed of a UmuD' homodimer and a UmuC monomer, forming the UmuD'2C protein complex. It is part of the Y-family of DNA Polymerases, which are capable of performing DNA translesion synthesis (TLS). Translesion polymerases bypass DNA damage lesions during DNA replication - if a lesion is not repaired or bypassed the replication fork can stall and lead to cell death. However, Y polymerases have low sequence fidelity during replication. When the UmuC and UmuD' proteins were initially discovered in E. coli, they were thought to be agents that inhibit faithful DNA replication and caused DNA synthesis to have high mutation rates after exposure to UV-light. The polymerase function of Pol V was not discovered until the late 1990s when UmuC was successfully extracted, consequent experiments unequivocally proved UmuD'2C is a polymerase. This finding lead to the detection of many Pol V orthologs and the discovery of the Y-family of polymerases.

<span class="mw-page-title-main">GrpE</span> InterPro Family

GrpE is a bacterial nucleotide exchange factor that is important for regulation of protein folding machinery, as well as the heat shock response. It is a heat-inducible protein and during stress it prevents unfolded proteins from accumulating in the cytoplasm. Accumulation of unfolded proteins in the cytoplasm can lead to cell death.

References

  1. 1 2 3 4 5 6 7 8 9 Foster JB, Slonczewski J (2009). Microbiology: an evolving science. New York: W.W. Norton & Co. ISBN   978-0-393-97857-5.
  2. 1 2 Hansen, Flemming G.; Atlung, Tove (2018-02-28). "The DnaA Tale". Frontiers in Microbiology. 9: 319. doi: 10.3389/fmicb.2018.00319 . ISSN   1664-302X. PMC   5835720 . PMID   29541066.
  3. 1 2 Hansen FG, Atlung T (2018-02-28). "The DnaA Tale". Frontiers in Microbiology. 9: 319. doi: 10.3389/fmicb.2018.00319 . PMC   5835720 . PMID   29541066.
  4. Leonard AC, Grimwade JE (December 2010). "Regulating DnaA complex assembly: it is time to fill the gaps". Current Opinion in Microbiology. 13 (6): 766–772. doi:10.1016/j.mib.2010.10.001. PMC   3005629 . PMID   21035377.
  5. Fuller RS, Funnell BE, Kornberg A (October 1984). "The dnaA protein complex with the E. coli chromosomal replication origin (oriC) and other DNA sites". Cell. 38 (3): 889–900. doi:10.1016/0092-8674(84)90284-8. PMID   6091903. S2CID   23316215.
  6. Costa A, Hood IV, Berger JM (2013-01-01). "Mechanisms for initiating cellular DNA replication". Annual Review of Biochemistry. 82: 25–54. doi:10.1146/annurev-biochem-052610-094414. PMC   4696014 . PMID   23746253.
  7. Roth A, Messer W (May 1995). "The DNA binding domain of the initiator protein DnaA". The EMBO Journal. 14 (9): 2106–2111. doi:10.1002/j.1460-2075.1995.tb07202.x. PMC   398312 . PMID   7744016.
  8. Ricard, Matthieu; Hirota, Yukinori (October 1973). "Process of Cellular Division in Escherichia coli : Physiological Study on Thermosensitive Mutants Defective in Cell Division". Journal of Bacteriology. 116 (1): 314–322. doi:10.1128/jb.116.1.314-322.1973. ISSN   0021-9193. PMC   246424 . PMID   4583216.
  9. Speck C, Weigel C, Messer W (November 1999). "ATP- and ADP-dnaA protein, a molecular switch in gene regulation". The EMBO Journal. 18 (21): 6169–6176. doi:10.1093/emboj/18.21.6169. PMC   1171680 . PMID   10545126.
  10. 1 2 Braun, Robert E.; O'Day, Kathy; Wright, Andrew (January 1985). "Autoregulation of the DNA replication gene dnaA in E. coli K-12". Cell. 40 (1): 159–169. doi:10.1016/0092-8674(85)90319-8. PMID   2981626. S2CID   10594994.
  11. Leonard, Alan C; Grimwade, Julia E (December 2010). "Regulating DnaA complex assembly: it is time to fill the gaps". Current Opinion in Microbiology. 13 (6): 766–772. doi:10.1016/j.mib.2010.10.001. PMC   3005629 . PMID   21035377.
  12. Katayama T, Kubota T, Kurokawa K, Crooke E, Sekimizu K (July 1998). "The initiator function of DnaA protein is negatively regulated by the sliding clamp of the E. coli chromosomal replicase". Cell. 94 (1): 61–71. doi: 10.1016/S0092-8674(00)81222-2 . PMID   9674428. S2CID   15215988.
  13. Kato J, Katayama T (August 2001). "Hda, a novel DnaA-related protein, regulates the replication cycle in Escherichia coli". The EMBO Journal. 20 (15): 4253–4262. doi:10.1093/emboj/20.15.4253. PMC   149159 . PMID   11483528.
  14. Kasho K, Katayama T (January 2013). "DnaA binding locus datA promotes DnaA-ATP hydrolysis to enable cell cycle-coordinated replication initiation". Proceedings of the National Academy of Sciences of the United States of America. 110 (3): 936–941. Bibcode:2013PNAS..110..936K. doi: 10.1073/pnas.1212070110 . PMC   3549119 . PMID   23277577.
  15. Fujimitsu K, Senriuchi T, Katayama T (May 2009). "Specific genomic sequences of E. coli promote replicational initiation by directly reactivating ADP-DnaA". Genes & Development. 23 (10): 1221–1233. doi:10.1101/gad.1775809. PMC   2685538 . PMID   19401329.
  16. Michelsen, Ole; Teixeira de Mattos, M. Joost; Jensen, Peter Ruhdal; Hansen, Flemming G. (2003-04-01). "Precise determinations of C and D periods by flow cytometry in Escherichia coli K-12 and B/r". Microbiology. 149 (4): 1001–1010. doi: 10.1099/mic.0.26058-0 . ISSN   1350-0872. PMID   12686642.
  17. 1 2 Morigen; Løbner-Olesen, Anders; Skarstad, Kirsten (2003-08-22). "Titration of the Escherichia coli DnaA protein to excess datA sites causes destabilization of replication forks, delayed replication initiation and delayed cell division: Destabilization of replication forks by excess datA". Molecular Microbiology. 50 (1): 349–362. doi: 10.1046/j.1365-2958.2003.03695.x . PMID   14507385. S2CID   21606647.
  18. Frimodt-Møller, Jakob; Charbon, Godefroid; Krogfelt, Karen A.; Løbner-Olesen, Anders (2016-09-02). Viollier, Patrick H. (ed.). "DNA Replication Control Is Linked to Genomic Positioning of Control Regions in Escherichia coli". PLOS Genetics. 12 (9): e1006286. doi:10.1371/journal.pgen.1006286. ISSN   1553-7404. PMC   5010248 . PMID   27589233.
  19. 1 2 Hansen, Egon B.; Atlung, Tove; Hansen, Flemming G.; Skovgaard, Ole; von Mevenburg, Kaspar (September 1984). "Fine structure genetic map and complementation analysis of mutations in the dnaA gene of Escherichia coli". Molecular and General Genetics. 196 (3): 387–396. doi:10.1007/BF00436184. ISSN   0026-8925. PMID   6094968. S2CID   3094956.
  20. Atlung, Tove; Clausen, Erik S.; Hansen, Flemming G. (August 1985). "Autoregulation of the dnaA gene of Escherichia coli K12". Molecular and General Genetics. 200 (3): 442–450. doi:10.1007/BF00425729. ISSN   0026-8925. PMID   2995766. S2CID   7623820.

Further reading

This article incorporates text from the public domain Pfam and InterPro: IPR013159
This article incorporates text from the public domain Pfam and InterPro: IPR013317