title: Distinct roles of a tyrosine-associated hydrogen-bond network in fine-tuning the structure and function of heme proteins: two cases designed for myoglobin.
abstract: A hydrogen-bond (H-bond) network, specifically a Tyr-associated H-bond network, plays key roles in regulating the structure and function of proteins, as exemplified by abundant heme proteins in nature. To explore an approach for fine-tuning the structure and function of artificial heme proteins, we herein used myoglobin (Mb) as a model protein and introduced a Tyr residue in the secondary sphere of the heme active site at two different positions (107 and 138). We performed X-ray crystallography, UV-Vis spectroscopy, stopped-flow kinetics, and electron paramagnetic resonance (EPR) studies for the two single mutants, I107Y Mb and F138Y Mb, and compared to that of wild-type Mb under the same conditions. The results showed that both Tyr107 and Tyr138 form a distinct H-bond network involving water molecules and neighboring residues, which fine-tunes ligand binding to the heme iron and enhances the protein stability, respectively. Moreover, the Tyr107-associated H-bond network was shown to fine-tune both H2O2 binding and activation. With two cases demonstrated for Mb, this study suggests that the Tyr-associated H-bond network has distinct roles in regulating the protein structure, properties and functions, depending on its location in the protein scaffold. Therefore, it is possible to design a Tyr-associated H-bond network in general to create other artificial heme proteins with improved properties and functions.
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001, China. linlinying@hotmail.com ywlin@usc.edu.cn.
authors.forename: Fei
authors.initials: F
authors.lastname: Liao
authors.forename: Hong
authors.initials: H
authors.lastname: Yuan
authors.forename: Ke-Jie
authors.initials: KJ
authors.lastname: Du
authors.forename: Yong
authors.initials: Y
authors.lastname: You
authors.forename: Shu-Qin
authors.initials: SQ
authors.lastname: Gao
authors.forename: Ge-Bo
authors.initials: GB
authors.lastname: Wen
authors.forename: Ying-Wu
authors.initials: YW
authors.lastname: Lin
authors.forename: Xiangshi
authors.initials: X
authors.lastname: Tan
mesh_terms: D018360:Crystallography, X-Ray; D006418:Heme / Q000737:chemistry*; D006860:Hydrogen Bonding; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D058767:Protein Unfolding; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D008024:Ligands; D009211:Myoglobin; D014443:Tyrosine; D006418:Heme; D006861:Hydrogen Peroxide