PTS L-Ascorbate Family

Last updated
Phosphotransferase permease
Identifiers
SymbolPTS
Pfam PF03611
InterPro IPR004703
TCDB 4.A.7
OPM superfamily 426
OPM protein 5zov
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary

The PTS L-Ascorbate (L-Asc) Family (TC# 4.A.7) includes porters specific for L-ascorbate, and is part of the PTS-AG superfamily. A single PTS permease of the L-Asc family of PTS permeases has been functionally characterized. This is the SgaTBA system, renamed UlaABC (utilization of L-ascorbate) by Yew and Gerlt. [1] [2]

Contents

The SgaTBA System

The SgaTBA permease consists of three proteins: SgaT, SgaB, and SgaA. SgaT is a 12 TMS protein, possibly very distantly related to the MFS hexuronate permease of Escherichia coli (TC# 2.A.1.14.2), which presumably functions as a PTS IIC protein. [3] [4] This gene product, as well as SgaB and SgaA, are all essential for anaerobic L-ascorbate utilization, transport and phosphorylation. [5] This is the first documented example where the two sugar-specific energy-coupling proteins of a PTS permease are more closely related to the proteins of two different families. The sga regulation is controlled by the nearby YjfQ repressor. [5] [6]

Homology

Homologues of SgaT, like other PTS protein homologues, have been identified in a large number of evolutionarily divergent bacteria, but not in archaea or eukaryotes. [5] Bacteria that encode SgaT homologues include numerous Gram-negative Pseudomonadota, as well as many low and high G+C Gram-positive bacteria. Except for species of Corynebacterium, Streptomyces , and Bacillus, almost all organisms possessing SgaTBA homologues are human/animal pathogens.

Several organisms have two or more SgaT paralogues, including E. coli, which has three. In some of the homologues found in other bacteria, SgaB domains are fused C-terminal to the SgaT domains. For example, this is true of putative transporters in Vibrio cholerae , Pasteurella multocida and Mycoplasma pulmonis. Homologues of SgaB and SgaA, but not SgaT, are also found in transcriptional activator proteins where they function in regulation rather than sugar transport. [7]

Transport Reaction

The group translocation reaction catalyzed by SgaTBA is:

L-ascorbate (out) → L-ascorbate-6-phosphate (in)

Related Research Articles

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<span class="mw-page-title-main">O-succinylbenzoate synthase</span>

o-Succinylbenzoate synthase (OSBS) (EC 4.2.1.113) is an enzyme encoded by the menC gene in E.coli, and catalyzes the dehydration of 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) to form 4-(2'-carboxyphenyl)-4-oxobutyrate, also called o-succinylbenzoate or OSB, hence the name of the enzyme. This reaction is the fourth step in the menaquinone biosynthetic pathway, which is used by bacteria to synthesize menaquinone, also known as vitamin K2.

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The potassium (K+) uptake permease (KUP) family (TC# 2.A.72) is a member of the APC superfamily of secondary carriers. Proteins of the KUP/HAK/KT family include the KUP (TrkD) protein of E. coli and homologues in both Gram-positive and Gram-negative bacteria. High affinity (20 μM) K+ uptake systems (Hak1, TC# 2.A.72.2.1) of the yeast Debaryomyces occidentalis as well as the fungus, Neurospora crassa, and several homologues in plants have been characterized. Arabidopsis thaliana and other plants possess multiple KUP family paralogues. While many plant proteins cluster tightly together, the Hak1 proteins from yeast as well as the two Gram-positive and Gram-negative bacterial proteins are distantly related on the phylogenetic tree for the KUP family. All currently classified members of the KUP family can be found in the Transporter Classification Database.

The multidrug/oligosaccharidyl-lipid/polysaccharide (MOP) flippase superfamily is a group of integral membrane protein families. The MOP flippase superfamily includes twelve distantly related families, six for which functional data are available:

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  4. One (MVF) lipid-peptidoglycan precursor flippase involved in cell wall biosynthesis - (TC# 2.A.66.4) The Mouse Virulence Factor (MVF) Family
  5. One (AgnG) which includes a single functionally characterized member that extrudes the antibiotic, Agrocin 84 - (TC# 2.A.66.5) The Agrocin 84 Antibiotic Exporter (AgnG) Family
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The Disulfide bond oxidoreductase D (DsbD) family is a member of the Lysine Exporter (LysE) Superfamily. A representative list of proteins belonging to the DsbD family can be found in the Transporter Classification Base.

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The p-aminobenzoyl-glutamate transporter(AbgT) family (TC# 2.A.68) is a family of transporter proteins belonging to the ion transporter (IT) superfamily. The AbgT family consists of the AbgT (YdaH; TC# 2.A.68.1.1) protein of E. coli and the MtrF drug exporter (TC# 2.A.68.1.2) of Neisseria gonorrhoeae. The former protein is apparently cryptic in wild-type cells, but when expressed on a high copy number plasmid, or when expressed at higher levels due to mutation, it appeared to allow uptake (Km = 123 nM; see Michaelis–Menten kinetics) and subsequent utilization of p-aminobenzoyl-glutamate as a source of p-aminobenzoate for p-aminobenzoate auxotrophs. p-Aminobenzoate is a constituent of and a precursor for the biosynthesis of folic acid. MtrF was annotated as a putative drug efflux pump.

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The PTSGlucose-Glucoside (Glc) family includes porters specific for glucose, glucosamine, N-acetylglucosamine and a large variety of α- and β-glucosides, and is part of the PTS-GFL superfamily.

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Permease of phosphotransferase system is a superfamily of phosphotransferase enzymes that facilitate the transport of L-ascorbate (A) and galactitol (G). Classification has been established through phylogenic analysis and bioinformatics.

The PTS Mannose-Fructose-Sorbose (Man) Family is a group of multicomponent PTS systems that are involved in sugar uptake in bacteria. This transport process is dependent on several cytoplasmic phosphoryl transfer proteins - Enzyme I (I), HPr, Enzyme IIA (IIA), and Enzyme IIB (IIB) as well as the integral membrane sugar permease complex (IICD). It is not part of the PTS-AG or PTS-GFL superfamilies.

References

  1. ↑ Tchieu JH, Norris V, Edwards JS, Saier MH (July 2001). "The complete phosphotransferase system in Escherichia coli". Journal of Molecular Microbiology and Biotechnology. 3 (3): 329–46. PMID   11361063.
  2. ↑ Yew WS, Gerlt JA (January 2002). "Utilization of L-ascorbate by Escherichia coli K-12: assignments of functions to products of the yjf-sga and yia-sgb operons". Journal of Bacteriology. 184 (1): 302–6. doi:10.1128/jb.184.1.302-306.2002. PMC   134747 . PMID   11741871.
  3. ↑ Luo P, Yu X, Wang W, Fan S, Li X, Wang J (March 2015). "Crystal structure of a phosphorylation-coupled vitamin C transporter". Nature Structural & Molecular Biology. 22 (3): 238–41. doi:10.1038/nsmb.2975. PMID   25686089. S2CID   9955621.
  4. ↑ Luo P, Dai S, Zeng J, Duan J, Shi H, Wang J (2018). "Inward-facing conformation of l-ascorbate transporter suggests an elevator mechanism". Cell Discovery. 4: 35. doi:10.1038/s41421-018-0037-y. PMC   6048161 . PMID   30038796.
  5. 1 2 3 Zhang Z, Aboulwafa M, Smith MH, Saier MH (April 2003). "The ascorbate transporter of Escherichia coli". Journal of Bacteriology. 185 (7): 2243–50. doi:10.1128/jb.185.7.2243-2250.2003. PMC   151508 . PMID   12644495.
  6. ↑ Campos E, Aguilar J, Baldoma L, Badia J (November 2002). "The gene yjfQ encodes the repressor of the yjfR-X regulon (ula), which is involved in L-ascorbate metabolism in Escherichia coli". Journal of Bacteriology. 184 (21): 6065–8. doi:10.1128/jb.184.21.6065-6068.2002. PMC   135402 . PMID   12374842.
  7. ↑ Greenberg DB, Stülke J, Saier MH (October 2002). "Domain analysis of transcriptional regulators bearing PTS regulatory domains". Research in Microbiology. 153 (8): 519–26. doi:10.1016/s0923-2508(02)01362-1. PMID   12437213.

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