FOLDING PROPERTIES OF IRON-SULFUR PROTEINS

The H-1 NMR spectra in water of HiPIP I from Ectothiorhodospira haloph ila, the Cys77Ser mutant of the HiPIP from Chromatium vinosum, the 7Fe 8S ferredoxin from Bacillus schlegelii, the 8Fe8S ferredoxin from Clos tridium pasteurianum and the 2Fe2S ferredoxin from P. umbilicalis have been recorded with increasing amounts of guanidinium chloride. The Hi PIP I from E. halophila shows evidence of an intermediate state with t he cluster bound to a largely unfolded protein. To a smaller extent th is holds for the Cys77 Ser mutant of C. vinosum HiPIP and for the 8Fe8 S protein from C. pasteurianum ferredoxin. In the case of 7Fe8S and 2F e2S ferredoxins, guanidinium chloride causes loss of the cluster. It a ppears that the possibility of observing the intermediate state is rel ated to the role of the clusters in stabilizing the overall structure of the protein. (C) 1998 Elsevier Science S.A. All rights reserved.