PTS Glucitol Family

Last updated April 30, 2019

The PTS Glucitol (Gut) Family (TC# 4.A.4)consists only of glucitol-specific porters, but these occur both in Gram-negative and Gram-positive bacteria. It is part of the PTS-GFL superfamily.

Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.

Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.

The phosphotransferases system (PTS-GFL) superfamily is a superfamily of phosphotransferase enzymes that facilitate the transport of glucose, glucitol (G), fructose (F) and lactose (L). Classification has been established through phylogenic analysis and bioinformatics.

Structure

II^Gut of Escherichia coli consists of three proteins, a IIA protein, a putative 4 TMS IIC2 protein and a putative 4 TMS IIC1 protein.^[1] The N- and C-termini as well as the IIB domain may thereby be localized to the cell cytoplasm, but the topology has not been established experimentally. IIA^Gut is believed to be phosphorylated on a histidyl residue, while IIB^Gut is probably phosphorylated on a cysteyl residue. However, these possibilities have not been demonstrated experimentally.

Escherichia coli, also known as E. coli, is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination. The harmless strains are part of the normal microbiota of the gut, and can benefit their hosts by producing vitamin K₂, and preventing colonization of the intestine with pathogenic bacteria, having a symbiotic relationship. E. coli is expelled into the environment within fecal matter. The bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly afterwards.

Related Research Articles

Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules. They are present in the outer membrane of gram-negative bacteria and some gram-positive Mycobacteria, the outer membrane of mitochondria, and the outer chloroplast membrane.

PEP group translocation, also known as the phosphotransferase system or PTS, is a distinct method used by bacteria for sugar uptake where the source of energy is from phosphoenolpyruvate (PEP). It is known as multicomponent system that always involves enzymes of the plasma membrane and those in the cytoplasm. The PTS system uses active transport. After the translocation across the membrane, the metabolites transported are modified. The system was discovered by Saul Roseman in 1964. The bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) transports and phosphorylates its sugar substrates in a single energy-coupled step. 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 (IIC).The PTS Enzyme II complexes are derived from independently evolving 4 PTS Enzyme II complex superfamilies, that include the (1) Glucose (Glc),(2) Mannose (Man), (3) Ascorbate-Galactitol (Asc-Gat) and (4) Dihydroxyacetone (Dha) superfamilies.

The Nucleobase:Cation Symporter-1 (NCS1) Family (TC# 2.A.39) consists of over 1000 currently sequenced proteins derived from Gram-negative and Gram-positive bacteria, archaea, fungi and plants. These proteins function as transporters for nucleobases including purines and pyrimidines. Members of this family possess twelve transmembrane α-helical spanners (TMSs). At least some of them have been shown to function in uptake by substrate:H⁺ symport mechanism.

Holins are a diverse group of small proteins produced by dsDNA bacteriophages in order to trigger and control the degradation of the host's cell wall at the end of the lytic cycle. Holins form pores in the host's cell membrane, allowing lysins to reach and degrade peptidoglycan, a component of bacterial cell walls. Holins have been shown to regulate the timing of lysis with great precision. Over 50 unrelated gene families encode holins, making them the most diverse group of proteins with common function. Together with lysins, holins are being studied for their potential use as antibacterial agents.

Divalent anion:Na⁺ symporters were found in bacteria, archaea, plant chloroplasts and animals.

The 6TMS Neutral Amino Acid Transporter (NAAT) Family is a family of transporters belonging to the Lysine Exporter (LysE) Superfamily. Homologues are found in numerous Gram-negative and Gram-positive bacteria including many human pathogens. Several archaea also encode MarC homologues. Some of these organisms have 2 or more paralogues. Most of these proteins are of about the same size although a few are larger. They exhibit 6 putative TMSs. A representative list of members belonging to the NAAT family can be found in the Transporter Classification Database.

The 2 or 3 TMS Putative Holin Family consists of many proteobacterial proteins ranging in size from about 70 to 120 amino acyl residues (aas) in length that exhibit 2 or 3 predicted transmembrane segments (TMSs). Although annotated as holins, these proteins are not yet functionally characterized. A representative list of proteins belonging to the 2/3 Holin family can be found in the Transporter Classification Database.

The Putative 3-4 TMS Transglycosylase-associated Holin Family is believed to be a group of holins that does not belong to one of the seven holin superfamilies. Homologues include thousands of diverse phage and bacterial proteins between 80 and 140 amino acyl residues (aas) in length that exhibit 3 to 4 transmembrane segments (TMSs). These proteins are holin-like in their size and topology and are designated 'Transglycosylase-associated', 'Putative holin', 'Phage-like transmembrane protein', 'YeaQ protein', etc. in the NCBI protein database. As of early 2016, they remain functionally uncharacterized. They derive from a wide range of bacterial and archaeal phyla including both Gram-negative and Gram-positive bacteria. These proteins are related to the RDD family in the conserved domain database. A representative list of proteins belonging to the T-A Hol family can be found in the Transporter Classification Database.

The Putative Treponema 4 TMS Holin (Tre4Hol) Family consists of several proteins from Treponema species. They range in size from 100 to 110 amino acyl residues (aas) in length and exhibit 4 transmembrane segments (TMSs). A fragment has been sequenced from Treponema phage Phi td1 (D2ECI8) and was designated a putative holin.

The Putative Listeria Phage Holin (LP-Hol) Family consists of several small proteins of 41 amino acyl residues (aas) and 1 transmembrane segment (TMS). They can be found in several Listeria phage as well as in Listeria monocytogenes. While annotated as holins, these proteins remain functionally uncharacterized. A representative list of proteins belonging to the LP-Hol family can be found in the Transporter Classification Database.

The Putative 3 TMS Holin (3-Hol) Family is large, consisting of many members derived from proteobacteria and their phage, all of small size and usually with 3 transmembrane segments (TMSs). A representative list of the proteins belonging to this family can be found in the Transporter Classification Database. While many of the proteins belonging to this family are annotated in holins, they remain functionally uncharacterized.

The Putative Archaeal 2 TMS Holin (A2-Hol) Family consists of a few putative holins from Thaumarchaeota ranging in size from about 130 to 165 amino acyl residues (aas) and exhibiting 2 transmembrane segments (TMSs). A representative list of proteins belonging to the A2-Hol family can be found in the Transporter Classification Database. The archaeon, Candidatus Nitrosoarchaeum limnia, encodes adjacent genes designated Toxin Secretion/Lysis Holin. The "toxin" gene encodes a soluble protein of 325 aas stated as belonging to the "Glycosyltransferase GBT-type Superfamily". This protein brings up other glycosyltransferases in a NCBI BLAST search. The adjacent gene encodes a small protein of 132 aas and 2 TMSs that could be a holin, based on its size and topology. This protein has the UniProt accession number of S2E3C4. Paralogues are found in this same organism and other closely related species.

The BhlA Holin Family is named after putative holin-like peptides encoded in bacteria with bacteriocin similarities. BhlA proteins are generally about 67 to 80 amino acyl residues (aas) in length and exhibit a single N-terminal transmembrane segment (TMS). BhlA. It has an antibacterial activity against Gram-positive bacteria. A representative list of proteins belonging to this family can be found in the Transporter Classification Database.

The K⁺Transporter (Trk) Family is a member of the voltage-gated ion channel (VIC) superfamily. The proteins of the Trk family are derived from Gram-negative and Gram-positive bacteria, yeast and plants.

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.

The PTS Fructose-Mannitol (Fru) Family is a large and complex family that is part of the PTS-GFL superfamily. It includes several sequenced fructose, mannose and mannitol-specific porters, as well as several putative PTS porters of unknown specificities. The fructose porters of this family phosphorylate fructose on the 1-position. Those of TC family 4.A.6 phosphorylate fructose on the 6-position.

The PTS Lactose-N,N’-Diacetylchitobiose (Lac) Family includes several sequenced lactose porters of Gram-positive bacteria, as well as the Escherichia coli and Borrelia burgdorferi N,N'-diacetylchitobiose (Chb) porters. It is part of the PTS-GFL superfamily. The former can transport aromatic β-glucosides and cellobiose, as well as Chb. However, only Chb induces expression of the chb operon.

The PTS L-Ascorbate (L-Asc) Family 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 by Yew and Gerlt.

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

↑ Nguyen, Thai X.; Yen, Ming-Ren; Barabote, Ravi D.; Saier, Milton H. (2006-01-01). "Topological predictions for integral membrane permeases of the phosphoenolpyruvate:sugar phosphotransferase system". Journal of Molecular Microbiology and Biotechnology. 11 (6): 345–360. doi:10.1159/000095636. ISSN 1464-1801. PMID 17114898.

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[1] Nguyen, Thai X.; Yen, Ming-Ren; Barabote, Ravi D.; Saier, Milton H. (2006-01-01). "Topological predictions for integral membrane permeases of the phosphoenolpyruvate:sugar phosphotransferase system". Journal of Molecular Microbiology and Biotechnology. 11 (6): 345–360. doi:10.1159/000095636. ISSN 1464-1801. PMID 17114898.