PMID:15654077
| Citation |
Tang, C, Williams, DC Jr, Ghirlando, R and Clore, GM (2005) Solution structure of enzyme IIA(Chitobiose) from the N,N'-diacetylchitobiose branch of the Escherichia coli phosphotransferase system. J. Biol. Chem. 280:11770-80 |
|---|---|
| Abstract |
The solution structure of trimeric Escherichia coli enzyme IIA(Chb) (34 kDa), a component of the N,N'-diacetylchitobiose/lactose branch of the phosphotransferase signal transduction system, has been determined by NMR spectroscopy. Backbone residual dipolar couplings were used to provide long range orientational restraints, and long range (|i - j| > or = 5 residues) nuclear Overhauser enhancement restraints were derived exclusively from samples in which at least one subunit was 15N/13C/2H/(Val-Leu-Ile)-methyl-protonated. Each subunit consists of a three-helix bundle. Hydrophobic residues lining helix 3 of each subunit are largely responsible for the formation of a parallel coiled-coil trimer. The active site histidines (His-89 from each subunit) are located in three symmetrically placed deep crevices located at the interface of two adjacent subunits (A and C, C and B, and B and A). Partially shielded from bulk solvent, structural modeling suggests that phosphorylated His-89 is stabilized by electrostatic interactions with the side chains of His-93 from the same subunit and Gln-91 from the adjacent subunit. Comparison with the x-ray structure of Lactobacillus lactis IIA(Lac) reveals some substantial structural differences, particularly in regard to helix 3, which exhibits a 40 degrees kink in IIA(Lac) versus a 7 degrees bend in IIA(Chb). This is associated with the presence of an unusually large (230-angstroms3) buried hydrophobic cavity at the trimer interface in IIA(Lac) that is reduced to only 45 angstroms3) in IIA(Chb). |
| Links |
PubMed Online version:10.1074/jbc.M414300200 |
| Keywords |
Amino Acid Sequence; Binding Sites; Disaccharides/chemistry; Escherichia coli/enzymology; Escherichia coli Proteins/chemistry; Light; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Phosphotransferases/chemistry; Scattering, Radiation; Solutions |
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