title: Time-dependent atomic coordinates for the dissociation of carbon monoxide from myoglobin.
abstract: Picosecond time-resolved crystallography was used to follow the dissociation of carbon monoxide from the heme pocket of a mutant sperm whale myoglobin and the resultant conformational changes. Electron-density maps have previously been created at various time points and used to describe amino-acid side-chain and carbon monoxide movements. In this work, difference refinement was employed to generate atomic coordinates at each time point in order to create a more explicit quantitative representation of the photo-dissociation process. After photolysis the carbon monoxide moves to a docking site, causing rearrangements in the heme-pocket residues, the coordinate changes of which can be plotted as a function of time. These include rotations of the heme-pocket phenylalanine concomitant with movement of the distal histidine toward the solvent, potentially allowing carbon monoxide movement in and out of the protein and proximal displacement of the heme iron. The degree of relaxation toward the intermediate and deoxy states was probed by analysis of the coordinate movements in the time-resolved models, revealing a non-linear progression toward the unbound state with coordinate movements that begin in the heme-pocket area and then propagate throughout the rest of the protein.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison, USA.
authors.forename: Roman
authors.initials: R
authors.lastname: Aranda
authors.forename: Elena J
authors.initials: EJ
authors.lastname: Levin
authors.forename: Friedrich
authors.initials: F
authors.lastname: Schotte
authors.forename: Philip A
authors.initials: PA
authors.lastname: Anfinrud
authors.forename: George N
authors.initials: GN
authors.lastname: Phillips
mesh_terms: D000465:Algorithms; D000818:Animals; D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray / Q000379:methods*; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010782:Photolysis; D011485:Protein Binding / Q000528:radiation effects; D011487:Protein Conformation; D050661:Sperm Whale / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D009211:Myoglobin; D006418:Heme; D002248:Carbon Monoxide