title: A distal tyrosine residue is required for ligand discrimination in DevS from Mycobacterium tuberculosis.
abstract: DevS is a heme-based sensor kinase required for sensing environmental conditions leading to nonreplicating persistence in Mycobacterium tuberculosis. Kinase activity is observed when the heme is a ferrous five-coordinate high-spin or six-coordinate low-spin CO or NO complex but is strongly inhibited in the oxy complex. Discrimination between these exogenous ligands has been proposed to depend on a specific hydrogen bond network with bound oxygen. Here we report resonance Raman data and autophosphorylation assays of wild-type and Y171F DevS in various heme complexes. The Y171F mutation eliminates ligand discrimination for CO, NO, and O2, resulting in equally inactive complexes. In contrast, the ferrous-deoxy Y171F variant exhibits autokinase activity equivalent to that of the wild type. Raman spectra of the oxy complex of Y171F indicate that the environment of the oxy group is significantly altered from that in the wild type. They also suggest that a solvent molecule in the distal pocket substitutes for the Tyr hydroxyl group to act as a poorer hydrogen bond donor to the oxy group. The wild-type CO and NO complexes exist as a major population in which the CO or NO groups are free of hydrogen bonds, while the Y171F mutation results in a mild increase in the distal pocket polarity. The Y171F mutation has no impact on the proximal environment of the heme, and the activity observed with the five-coordinate ferrous-deoxy wild type is conserved in the Y171F variant. Thus, while the absence of an exogenous ligand in the ferrous-deoxy proteins leads to a moderate kinase activity, interactions between Tyr171 and distal diatomic ligands turn the kinase activity on and off. The Y171F mutation disrupts the on-off switch and renders all states with a distal ligand inactive. This mechanistic model is consistent with Tyr171 being required for distal ligand discrimination, but nonessential for autophosphorylation activity.
authors.affiliation: Department of Environmental and Biomolecular Systems, OGI School of Science and Engineering, Oregon Health and Science University, 20000 NW Walker Road, Beaverton, Oregon 97006-8921, USA.
authors.forename: Erik T
authors.initials: ET
authors.lastname: Yukl
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ioanoviciu
authors.forename: Michiko M
authors.initials: MM
authors.lastname: Nakano
authors.forename: Paul R Ortiz
authors.initials: PR
authors.lastname: de Montellano
authors.forename: Pierre
authors.initials: P
authors.lastname: Moënne-Loccoz
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D009154:Mutation; D009169:Mycobacterium tuberculosis; D010766:Phosphorylation; D006656:Protamine Kinase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman; D013379:Substrate Specificity; D014443:Tyrosine
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D014443:Tyrosine; C506260:DevS protein, Mycobacterium tuberculosis; D006656:Protamine Kinase