CONFORMATIONAL STATES OF HEMOPROTEINS BY XANES - THE MUTANT VR MYOGLOBIN

We have measured the Fe K-XANES spectrum of a site directed double mut ant myoglobin (VR Mb), where distal His(E7) is substituted by Val and Thr(E10) is substituted by Arg, at ESRF (Grenoble, France) in fluoresc ence mode, by using the ultra-pure Ge 13-element array detector by Can berra Industries. A change of the coordination symmetry at the Fe site induced by changing the two aminoacids in the distal side has been pr obed. Evidence that water is not bound to the iron site in the acid fe rric myoglobin has been found. The result is in accord with previous N MR and optical spectroscopic data, suggesting that Arg(E10) is out of the heme pocket in acid ferric VR myoglobin.