Neutral complexes as oxidants for the reduced form of parsley (Petroselinum crispum) [2Fe-2S] ferredoxin. Evidence for partial blocking by redox-inactive Cr(III) complexes

Publisher Website
Google Scholar
Abstract
The 1:1 reactions of 3 neutral Co(III) oxidants, Co(acac [acetylacetone])3, Co(NH3)3(NO2)3 and Co(acac)2(NH3)(NO2), with reduced parsley (P. crispum) [2Fe-2S] ferredoxin (which carries a substantial negative charge), were studied at 25.degree. C, pH 8.0 (Tris/HCl), I0.10 (NaCl). With Co(NH3)6+ as oxidant, the reaction is completely blocked by redox-inactive Cr(NH3)63+, the neutral oxidants are only partially blocked by this same complex. The effects of 3 Cr(III) complexes, Cr(NH3)63+, Cr(en [ethylenediamine])33+ and (en)2Cr.cntdot..mu.(OH,O2CCH3).cntdot.Cr(en)24+ were investigated. Kinetic data for the response of 3+, neutral, as well as 1- oxidants to the presence of 3+ (and 4+) Cr(III) complex can now be rationalized in terms of a single functional site on the protein for electron transfer. Electrostatics have a significant influence on association at this site.