J. Biol. Chem., Vol. 269, Issue 15, 11196-11200, 04, 1994
Identical mutations at corresponding positions in two homologous proteins with nonidentical effects
AJ Bjorkman, RA Binnie, LB Cole, H Zhang, MA Hermodson and SL Mowbray
Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala.
The x-ray structure of a mutant (Gly72 to Asp) of the Escherichia coli
ribose-binding protein with altered transport function has been solved and
refined to 2.2-A resolution with a conventional R-factor (R-factor =
[formula: see text]) of 16.0% and good stereochemistry. Comparison with the
wild type ribose-binding protein shows that the structure is disturbed
little at the actual mutation site, but quite appreciably in a neighboring
loop. Changes in the surface of the protein at the site of mutation,
however, seem to explain the functional effects. A corresponding mutation
of the related glucose/galactose-binding protein has different structural
and functional effects due to the different structural context of the
mutation site in that protein. These results are consistent with the
concept that these proteins have slightly different ways of interacting
with the membrane components in transport and chemotaxis.