PTS Mannose-Fructose-Sorbose Family

The PTS Mannose-Fructose-Sorbose (Man) Family (TC# 4.A.6) 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.

Distinguishing characteristics from other PTS porters

The Man Family is unique in several respects among other PTS porter families:

  1. It is the only PTS family in which members possess a IID protein;
  2. It is the only PTS family in which the IIB constituent is phosphorylated on a histidyl rather than a cysteyl residue;[1]
  3. Its porter members usually exhibit broad specificity for a range of sugars, rather than being specific for just one or a few sugars.

The mannose porter of Escherichia coli, for example, can transport and phosphorylate glucose, mannose, fructose, glucosamine, N-acetylglucosamine, and N-acteylmannosamine.[2]

Structure

The structure of the E. coli IIAMan domain has been shown to exhibit an α/β doubly wound superfold.[3] The IIB domain also exhibits an α/β doubly wound superfold, but it is very dissimilar from that of the IIA domain.[4] Instead, it has the same topology as phosphoglyceromutase (PGM). Since both proteins (IIBMan and PGM) catalyze phosphoryl transfer with a phosphohistidine intermediate, both proteins show a similar distribution of active site residues, and both exhibit similar structures, they are probably homologous.

IICMan of E. coli has been reported to have six transmembrane α-helical segments, while IIDMan was reported to have only one.[5][6] However, hydropathy plots show multiple peaks of hydropathy, rendering the experimental result, suggesting 1 TMS, questionable.[7] These two proteins together are required for transport, although IICMan is presumed to comprise all or most of the sugar transporting channel.

Transport reaction

The generalized reaction catalyzed by members of the Man Family is:

Sugar (out) + PEP (in) → Sugar-P (in) + pyruvate (in)

References
  1. Lengeler, Joseph W.; Drews, Gerhard; Schlegel, Hans G. (1999). Biology of Prokaryotes. Stuttgart, Germany: Blackwell Science. pp. 83–84. ISBN 978-0-632-05357-5.
  2. Plumbridge, Jacqueline (Jan 1999). "Convergent pathways for utilization of the amino sugars N-acetylglucosamine, N-acetylmannosamine, and N-acetylneuraminic acid by Escherichia coli". Journal of Bacteriology. 181 (1): 47–54. doi:10.1128/JB.181.1.47-54.1999. PMC 103530. PMID 9864311.
  3. Hu, Jun; Hu, Kaifeng; Williams, David C.; Komlosh, Michal E.; Cai, Mengli; Clore, G. Marius (2008-04-18). "Solution NMR Structures of Productive and Non-productive Complexes between the A and B Domains of the Cytoplasmic Subunit of the Mannose Transporter of the Escherichia coli Phosphotransferase System". Journal of Biological Chemistry. 283 (16): 11024–11037. doi:10.1074/jbc.M800312200. ISSN 0021-9258. PMC 2447639. PMID 18270202.
  4. Orriss, George L.; Erni, Bernhard; Schirmer, Tilman (2003-04-11). "Crystal structure of the IIB(Sor) domain of the sorbose permease from Klebsiella pneumoniae solved to 1.75A resolution". Journal of Molecular Biology. 327 (5): 1111–1119. doi:10.1016/s0022-2836(03)00215-8. ISSN 0022-2836. PMID 12662934.
  5. Liu, Xueli; Zeng, Jianwei; Huang, Kai; Wang, Jiawei (2019-06-17). "Structure of the mannose transporter of the bacterial phosphotransferase system". Cell Research. 29 (8): 680–682. doi:10.1038/s41422-019-0194-z. ISSN 1748-7838. PMC 6796895. PMID 31209249.
  6. Huang, Kai; Zeng, Jianwei; Liu, Xueli; Jiang, Tianyu; Wang, Jiawei (2021-04-06). "Structure of the mannose phosphotransferase system (man-PTS) complexed with microcin E492, a pore-forming bacteriocin". Cell Discovery. 7 (1): 20. doi:10.1038/s41421-021-00253-6. ISSN 2056-5968. PMC 8021565. PMID 33820910.
  7. Huber, F.; Erni, B. (1996-08-01). "Membrane topology of the mannose transporter of Escherichia coli K12". European Journal of Biochemistry. 239 (3): 810–817. doi:10.1111/j.1432-1033.1996.0810u.x. ISSN 0014-2956. PMID 8774730.

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