ISSN:
1432-1327
Keywords:
Key words Reduction potential
;
Rubredoxin
;
Square wave voltammetry
;
X-ray crystallography
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract The Pri sidechains of two adjacent valine residues, V8 and V44, define the surface of the rubredoxin from Clostridium pasteurianum and control access to its Fe(S-Cys)4 active site. To assess the effect of systematic change of the steric bulk of the alkyl sidechains, eight single and three double mutant proteins have been isolated which vary G (H), A (Me), V (Pri), L (Bui) and I (Bus) at those positions. X-ray crystal structures of the FeIII forms of the V44A and V44I proteins are reported. Positive shifts in reversible potential of up to 116 mV are observed and attributed to increased polarity around the Fe(S-Cys)4 site induced by (1) changes in protein backbone conformation driven by variation of the steric demands of the sidechain substituents and (2) changes in solvent access to the sidechains of ligands C9 and C42. Data for the V44A mutant show that a minor change in the steric requirements of a surface residue can introduce a NH···Sγ hydrogen bond at the active site and lead to a shift in potentialof +50 mV.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00010656
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