PMID:8262947
| Citation |
Stolz, B, Huber, M, Marković-Housley, Z and Erni, B (1993) The mannose transporter of Escherichia coli. Structure and function of the IIABMan subunit. J. Biol. Chem. 268:27094-9 |
|---|---|
| Abstract |
The mannose transporter of the bacterial phosphotransferase system consists of two transmembrane subunits (IICMan and IIDMan) and a hydrophilic subunit (IIABMan). IIABMan has two flexibly linked domains containing one phosphorylation site each and occurs as a dimer. Substrate transport is coupled to phosphorylation. The phosphoryl group is transferred from a phosphoryl carrier protein to His10 on IIA, hence to His175 on IIB and finally to the substrate. IIABMan mutants were analyzed in vitro for complementation, negative dominance, cysteine cross-linking and reactivity. Conclusions: (i) His10, Trp12, Lys48, and Ser72 form a functional unit (phosphorylation site 1); (ii) His86 on the IIA domain and His175 on the IIB domain of the same subunit form a functional unit (phosphorylation site 2); (iii) phosphoryl transfer can occur between His10 and His175 of the same as well as of different subunits and His86 is necessary for this transfer; (iv) the subunits in the dimer are interdependent; (v) The phosphorylation site mutant H175C is highly reactive toward thiol reagents and it forms extensive homo- and heterocross-links with other surface-exposed cysteines. The phosphorylation site mutant H10C is 1000-fold less reactive. The two residues might be in complementary locations, His10 buried in a concave, His175 exposed on a convex surface. |
| Links | |
| Keywords |
Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Biological Transport; Carrier Proteins/chemistry; Carrier Proteins/genetics; Carrier Proteins/metabolism; Cross-Linking Reagents; Cysteine/chemistry; Escherichia coli/metabolism; Genetic Complementation Test; Mannose/metabolism; Oxidation-Reduction; Phosphorylation; Phosphotransferases/metabolism; Point Mutation; Protein Conformation |
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