Analysis of fluorophore-labeled human cytochrome b5

Cytochrome b5 (b5) is a small accessory protein involved in several reactions. The interaction of b5 with its partner proteins, e.g., cytochrome P450 enzymes, has received much attention and has been the subject of numerous studies. In order to obtain further insights into protein-protein interactions of b5, we modified it with a green fluorophore, Alexa 488, which has a maleimide linker. The labeling was applied to both WT (without Cys) and the T70C mutant. This study revealed labeled sites in WT b5 and confirmed the Cys-selective labeling in the T70C mutant.