The Effects Of Glutamate/histidine In Heme Active Site On The Structure And Functions Of Myoglobin

Myoglobin(Mb), an oxygen carrier, is consist of 153 amino acids and a heme prothetic group. For a long time, Mb has been favored and widely used as a framework to study the relationship between structure and function of proteins, especially heme proteins, because of its small molecular weight, high stability and easy to purify with a high purity by genetic engineering and protein engineering. To probe the effects of glutamate and histidine in heme active site on the structure and functions of myoglobin, we introduced both a distal Glu29 and His43 in the heme distal site, i.e., L29E/F43 H Mb, which forms a novel distal hydrogen-bonding network and regulats the heme into a bis-His coordination state with native ligands, His64 and His93.This study focuses on the L29E/F43 H Mb mutant, with wild-type(WT) Mb and single mutant F43 H and L29 E Mb as controls. By combination of X-ray crystallography, fluoride binding kinetics and hydrogen peroxidase activiation kinetics, this study explores the effects of glutamate and histidine in heme active site on the structure and catalytic function of Mb. These studies reveal that a distal hydrogen-bonding network in Mb not only can regulate the coordination state, but also the whole conformation of heme proteins. The new approach of hydrogen-bonding network and the kinetic parameter in this study can better reflect structure-property-function relationship of myoglobin, which provides scientific instruction to the design and construction of protein molecules.