Evaluation of Solvent Accessibility to the [Fe4S4] Binding Pocket in Native and Tyr19 Mutant High Potential Iron Proteins by 1H−15N HMQC and 19F NMR Experiments

Abstract

The solvent accessibility of Chromatium vinosumhigh potential iron protein (HiPIP) has been investigated by use of (1)H-(15)N HMQC, and (19)F NMR spectroscopy. These NMR experiments indicate that solvent accessibility to the cluster core is similar, and minimal, for the reduced and oxidized states of native HiPIP, but increases significantly for mutant proteins (Tyr19Leu and Tyr19His). These results support a proposed role [Agarwal, A.; Li, D.; Cowan, J. A. Proc. Natl. Acad. Sci. U.S.A. 1995, 92, 9440-9444] for Tyr19 in maintaining hydrolytic stability of the [Fe(4)S(4)] cluster, and demonstrate a general strategy for mapping out the solvent accessibility of protein-bound metalloredox prosthetic centers.