The acid-base properties and kinetics of dissolution of the Fe 4S 4 cores of chromatium ferredoxin and high potential iron protein

Abstract

Summary The kinetics for the dissolution of Chromatium ferredoxin and High Potential Iron Protein have been compared (H o = −1.05 to pH = 7). Chromatium ferredoxin hydrolyzes via a mechanism following the kinetics A = + H + ⇄ AH - ↠ BH - ↠ C at constant pH. Initial absorbances describe a theoretical one proton titration curve corresponding to a pK a of 2.7 for AH − . Chromatium High Potential Iron Protein shows no titration behavior and hydrolyzes slowly in water. These results confirm the availability of the Fe 4 S 4 -cores of Chromatium ferredoxin as compared to that of High Potential Iron Protein. Further, these results establish similarities in the hydrolytic chemistry of protein bound Fe 4 S 4 -cores as compared to synthetic compounds of structure Fe 4 S 4 (SR) 4 = .