title: Myoglobin mutants giving the largest geminate yield in CO rebinding in the nanosecond time domain.
abstract: We have measured the rebinding of carbon monoxide (CO) to some distal mutants of myoglobin (Mb) in the time range from 10(-8) to 10(-1) s by flash photolysis, in which the photodissociated CO rebinds to the heme iron without escaping to the solvent water from the protein matrix. We have found that the double mutants [His64-->Val/Val68-->Thr (H64V/V68T) and His64-->Val/Val68-->Ser (H64V/V68S)] have an extremely large geminate yield (70-80%) in water at 5 degreesC, in contrast to the 7% of the geminate yield of wild-type Mb. The CO geminate yields for these two mutants are the largest in those of Mb mutants reported so far, showing that the two mutants have a unique heme environment that favors CO geminate rebinding. Comparing the crystal structures and 1H-NMR and vibrational spectral data of H64V/V68T and H64V/V68S with those of other mutants, we discuss factors that may control the nanosecond geminate CO rebinding and CO migration in the protein matrix.
authors.affiliation: Faculty of Science, Gakushuin University, Mejiro, Toshima-ku, Tokyo 170, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sugimoto
authors.forename: M
authors.initials: M
authors.lastname: Unno
authors.forename: Y
authors.initials: Y
authors.lastname: Shiro
authors.forename: Y
authors.initials: Y
authors.lastname: Dou
authors.forename: M
authors.initials: M
authors.lastname: Ikeda-Saito
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D009211:Myoglobin / Q000737:chemistry*; D010782:Photolysis; D011485:Protein Binding / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry; D013059:Spectrum Analysis, Raman
chemical_list: D009211:Myoglobin; D011994:Recombinant Proteins; D006418:Heme; D002248:Carbon Monoxide