title: Ultrafast ligand dynamics in the heme-based GAF sensor domains of the histidine kinases DosS and DosT from Mycobacterium tuberculosis.
abstract: The transcriptional regulator DosR from M. tuberculosis plays a crucial role in the virulence to dormancy transition of the pathogen. DosR can be activated by DosT and DosS, two histidine kinases with heme-containing sensor GAF domains, capable of diatomic ligand binding. To investigate the initial processes occurring upon ligand dissociation, we performed ultrafast time-resolved absorption spectroscopy of the isolated sensor domains ligated with O(2), NO, and CO. The results reveal a relatively closed heme pocket for both proteins. For DosT the yield of O(2) escape from the heme pocket on the picoseconds time scale upon photodissociation was found to be very low (1.5%), similar to other heme-based oxygen sensor proteins, implying that this sensor acts as an effective O(2) trap. Remarkably, this yield is an order of magnitude higher in DosS (18%). For CO, by contrast, the fraction of CO rebinding within the heme pocket is higher in DosS. Experiments with mutant DosT sensor domains and molecular dynamics simulations indicate an important role in ligand discrimination of the distal tyrosine, present in both proteins, which forms a hydrogen bond with heme-bound O(2). We conclude that despite their similarity, DosT and DosS display ligand-specific different primary dynamics during the initial phases of intraprotein signaling. The distal tyrosine, present in both proteins, plays an important role in these processes.
authors.affiliation: Laboratory for Optics and Biosciences, CNRS Ecole Polytechnique, 91128 Palaiseau, France. marten.vos@polytechnique.edu
authors.forename: Marten H
authors.initials: MH
authors.lastname: Vos
authors.forename: Latifa
authors.initials: L
authors.lastname: Bouzhir-Sima
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Lambry
authors.forename: Hao
authors.initials: H
authors.lastname: Luo
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Eaton-Rye
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ioanoviciu
authors.forename: Paul R
authors.initials: PR
authors.lastname: Ortiz de Montellano
authors.forename: Ursula
authors.initials: U
authors.lastname: Liebl
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods; D018360:Crystallography, X-Ray; D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism; D000071677:Histidine Kinase; D006860:Hydrogen Bonding; D008024:Ligands; D056004:Molecular Dynamics Simulation; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000472:pathogenicity; D006656:Protamine Kinase / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology; D014443:Tyrosine / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D006420:Hemeproteins; D008024:Ligands; D014443:Tyrosine; D011494:Protein Kinases; C506260:DevS protein, Mycobacterium tuberculosis; D006656:Protamine Kinase; D000071677:Histidine Kinase; C542862:DosT protein, Mycobacterium tuberculosis