Studies on the reconstitution of bovine erythrocyte superoxide dismutase: I. The presence of four divalent metal-binding sites on the apo protein which are different from the native sites

Abstract

1. 1. The extinction coefficient ( E 1 cm 1 % ) of metal-free protein at 258 nm is 0.85±10% based on Lowry determinations of solutions of bovine serum albumin. 2. 2. The two tyrosine residues of superoxide dismutase fluorescence at λ max = 320 nm when excited at λ max = 278 nm , and the empirical intensity of the emission is the same in both apo and native proteins. 3. 3. The binding of Cu 2+, Zn 2+ and Hg 2+ to apo protein has been studied by fluorescence, polarographic, and optical absorption methods. 4. 4. The apo protein may bind four each of these ions to independent sites which differ in an unknown manner from those of the native protein.