Vol. 62, No. 1, 1975 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS RESONANCE RAMAN SPECTROSCOPIC EVIDENCE FOR STRUCTURAL 2-* VARIATION AMONG BACTERIAL FERREDOXIN, HiPIP= and Fe4S4(SCH2Ph)4 J.~J. S-P. W. Tang,** T. G. Spiro,** C. Antanaitis,*** T. H. Moss, ...... R. H. Holm,**** T. Herskovitz,**** and L. E. Mortensen***** **Chemistry Department, Princeton University, Princeton, N.J. 08540 ***IBM Watson Research Center, Yorktown Heights, N.Y. 10598 ****Chemistry Department, Mass. Institute of Technology, Cambridge Mass. 02139 *****Purdue University, Lafayette, Indiana Received November 13, 1974 Summary. Resonance Raman spectra have been obtained for C. pasteurianum ferredoxin, Chromatium HiPIP and Fe4S4(SCHoPh)L 2-, all of which contain a cubane-like Fe-S cluster. They sh~w bands assignable to Fe-S stretching vibrations of both bridging and terminal sulfur atoms. The frequencies shift significantly among the three molecules, and an extra polarized band gives evidence of symmetry lowering in the proteins. The iron-sulfur electron transfer proteins continue to generate much biochemical interest (i), and considerable progress has been made in elucidating their structural chemistry. Particularly striking are the relationships which have emerged among the bacterial ferre- doxins, the high-potential iron protein (HiPIP) of Chromatium and the 2- synthetic clusters [Fe4S4(SR)4 ] (2-6). All three contain cubane- type iron-sulfur clusters in which the iron and sulfur atoms occupy alternating corners of an approximate cube, and each iron atom is additionally bound to a sulfur atom of a cysteine residue. The bacterial ferredoxins generally contain two such clusters which in the P. aerogenes protein are ~12~ apart (5). Some four-iron ferredoxins are also known (7). Within the current resolution of the protein structure determinations no significant *This study was supported by Public Health Service Grants GM 13498 for TGS and GM 19256 for RHH. Abbreviations used: Ph- phenyl; HiPIP - High-potential iron protein. Copyright © 1975 by Academic Press, Inc. All rights of reproduction in any form reserved.