The X‐ray crystal structure of human <scp>A15C</scp> neuroglobin reveals both native/de novo disulfide bonds and unexpected ligand‐binding sites
Shu‐Qin Gao, Hong Yuan, Xichun Liu, Lianzhi Li, Xiangshi Tan, Ge‐Bo Wen, Ying‐Wu Lin
Abstract
Human neuroglobin (Ngb) contains a heme group and three Cys residues (Cys46, Cys55, and Cys120) in the polypeptide chain. By introducing an additional Cys at position 15, the X-ray structure of A15C Ngb mutant was solved at a high resolution of 1.35 Å, which reveals the formation of both the native (C46C55) and the engineered (C15C120) disulfide bonds, likely playing a functional and structural role, respectively, according to the geometry analysis. Unexpectedly, 1,4-dioxane from the crystallization reagents was bound not only to the protein surface, but also to the heme distal pocket, providing insights into protein-ligand interactions for the globin and guiding the design of functional heme enzymes.