92 Abstracts

A(-)()5 CONSERVED CYSTEINE-LIGAND ELECI’RON-TRANSFER PATHWAYS IN

CONFORMATION AND CUPREDOXINS

Jane Han,a Joann Sanders-Loehr,a Thomas M. Loehr,a Elinor T. Adman,b and Hans C. Freemanc a Department of Chemical & Biological Sciences, Oregon Graduate Institute of Science and Technology, Beaverton, Oregon 97006-1999, b Department of Biological Structure, University of Washington, Seattle, Washington 9819.5, and c Department oj Inorganic Chemistry, University of Sydney, Sydney> N.S. W. 2006 Australia

The crystal structures of four cupredoxins (plastocyanin, pseudo- azurin, cucumber basic protein, and azurin) show highly conserved coplanarity of the Cu-S(Cys) “blue copper” chromophore that extends over the Cu-S,-C,-Ca-N atoms, The coplanarity of these atoms per-

Alcohol Dehydrogenase

/ Ascorbalp Oxidase , !

/ Amicyanin

Frequency, cm-l

mits extensive vibrational coup- ling of Y(CU-S) with &(S-C-C-N) and can, thus, account for the -? peaks observed in the 330- to 460~cm1 region of the resonance Raman spectra of these proteins [I]. Other cupredoxins including steiiiacyanin, rusticyanin, aura- cyanin, and amicyanin (whose high-resolution X-ray structures are not yet available) have the same set of vibrational modes, indicating congruence of their Cu-S(Cys) structures [Figure], Solvent exchange studies have shown that most of the peaks in this region shift in .D,Q. These shifts are assigned to hydrogen bonding of the S(Cvs) ligand, a feature also noted in the X-ray structures [2]. The appearance of conserved amino acids flanking the extended cysteinate ligand may be involved in electron transfer to and from the copper site in cupredoxins and in multi- copper oxidases having “‘blue copper” sites,

1. W.H. Woodruff, B.R. Dyer, J.R. Schoonover, in Biological ,4pplications of Raman Spectroscopy, Vol. 3, T.G. Spiro, ed., Wiley, NY, 1988, pp. 413-438

2. Y. Mino, T.M. Loehr. K. Wada, H. Matsubara, & 1. Sanders-Loehr, Biochemistry 26, 8059-8065 (1987)