EVALUATION OF SOLVENT ACCESSIBILITY TO THE [FE4S4] BINDING POCKET IN NATIVE AND TYR19 MUTANT HIGH-POTENTIAL IRON PROTEINS BY H-1-N-15 HMQC AND F-19 NMR EXPERIMENTS

The solvent accessibility of Chromatium vinosum high potential iron pr otein (HiPIP) has been investigated by use of H-1-N-15 HMQC, and F-19 NMR spectroscopy. These NMR experiments indicate that solvent accessib ility to the cluster core is similar, and minimal, for the reduced and oxidized states of native HiPIP, but increases significantly for muta nt 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, 99, 9440-9444] for Tyr19 in maintaining hydrolytic stability of the [Fe4S4] cluster, and demonstrate a general strategy for mapping ou t the solvent accessibility of protein-bound metalloredox prosthetic c enters.