PTS Mannose-Fructose-Sorbose Family explained

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:

It is the only PTS family in which members possess a IID protein;
It is the only PTS family in which the IIB constituent is phosphorylated on a histidyl rather than a cysteyl residue;^[1]
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 IIA^Man 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 (IIB^Man 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.

IIC^Man of E. coli has been reported to have six transmembrane α-helical segments, while IID^Man 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 IIC^Man 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)

Notes and References

Book: Biology of Prokaryotes. Lengeler. Joseph W.. Drews, Gerhard. Schlegel, Hans G.. Blackwell Science. 1999. 978-0-632-05357-5. Stuttgart, Germany. 83–84.
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. 10.1128/JB.181.1.47-54.1999. 9864311. 103530. 47–54.
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. en. 283. 16. 11024–11037. 10.1074/jbc.M800312200. 0021-9258. 2447639. 18270202. free .
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. 0022-2836. 12662934. 10.1016/s0022-2836(03)00215-8.
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. 10.1038/s41422-019-0194-z. 1748-7838. 31209249. 6796895. free.
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. 10.1038/s41421-021-00253-6. 2056-5968. 8021565. 33820910.
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. 0014-2956. 8774730. 10.1111/j.1432-1033.1996.0810u.x. free.