ISSN:
1432-1327
Keywords:
Key words Chromatium vinosum
;
Electrostatic effects
;
High-potential iron-sulfur protein
;
NMR spectroscopy
;
Reduction potential
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract The amide group between residues 78 and 79 of Chromatium vinosum high-potential iron-sulfur protein (HiPIP) is in close proximity to the Fe4S4 cluster of this protein and interacts via a hydrogen bond with Sγ of Cys77, one of the cluster ligands. The reduction potential of the S79P variant was 104±3 mV lower than that of the recombinant wild-type (rcWT) HiPIP (5 mM phosphate, 100 mM NaCl, pH 7, 293 K), principally due to a decrease in the enthalpic term which favors the reduction of the rcWT protein. Analysis of the variant protein by NMR spectroscopy indicated that the substitution has little effect on the structure of the HiPIP or on the electron distribution in the oxidized cluster. Potential energy calculations indicate that the difference in reduction potential between rcWT and S79P variant HiPIPs is due to the different electrostatic properties of amide 79 in these two proteins. These results suggest that the influence of amide group 79 on the reduction potential of C. vinosum HiPIP is a manifestation of a general electrostatic effect rather than a specific interaction. More generally, these results provide experimental evidence for the importance of buried polar groups in determining the reduction potentials of metalloproteins.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050341
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