<Emphasis Type="Italic">Corynebacterium diphtheriae</Emphasis> HmuT: dissecting the roles of conserved residues in heme pocket stabilization |
| |
Authors: | Elizabeth B Draganova Seth A Adrian Gudrun S Lukat-Rodgers Cyrianne S Keutcha Michael P Schmitt Kenton R Rodgers Dabney W Dixon |
| |
Institution: | 1.Department of Chemistry,Georgia State University,Atlanta,USA;2.Department of Chemistry and Biochemistry,North Dakota State University,Fargo,USA;3.Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products,Center for Biologics Evaluation, and Research, Food and Drug Administration,Silver Spring,USA |
| |
Abstract: | The heme-binding protein HmuT is part of the Corynebacterium diphtheriae heme uptake pathway and is responsible for the delivery of heme to the HmuUV ABC transporter. HmuT binds heme with a conserved His/Tyr heme axial ligation motif. Sequence alignment revealed additional conserved residues of potential importance for heme binding: R237, Y272 and M292. In this study, site-directed mutations at these three positions provided insight into the nature of axial heme binding to the protein and its effect on the thermal stability of the heme-loaded protein fold. UV–visible absorbance, resonance Raman (rR) and thermal unfolding experiments, along with collision-induced dissociation electrospray ionization mass spectrometry, were used to probe the contributions of each mutated residue to the stability of ? HmuT. Thermal unfolding and rR experiments revealed that R237 and M292 are important residues for heme binding. Arginine 237 is a hydrogen-bond donor to the phenol side chain of Y235, which serves as an axial heme ligand. Methionine 292 serves a supporting structural role, favoring the R237 hydrogen-bond donation, which elicits a, heretofore, unobserved modulating influence on π donation by the axial tyrosine ligand in the heme carbonyl complex, HmuT–CO. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|