CHARACTERIZATION OF A PARTIALLY UNFOLDED HIGH-POTENTIAL IRON PROTEIN

A partially unfolded state of the Fe4S4-containing high potential iron -sulfur protein from Chromatium vinosum has been detected and characte rized by NMR spectroscopy following addition of a concentrated solutio n of guanidinium chloride to the native protein. This intermediate spe cies (i) maintains the polymetallic center, (ii) exhibits a largely co llapsed secondary structure, and (iii) undergoes East cluster decompos ition upon oxidation. This information is framed into the knowledge ab out this class of proteins, and the possible role of this intermediate with respect to the in vivo folding/unfolding process is discussed as well its role in the slow hydrolytic degradation characteristic of ox idized HiPIPs.