title: Functional transitions in myosin: formation of a critical salt-bridge and transmission of effect to the sensitive tryptophan.
abstract: For analyzing the mechanism of energy transduction in the "motor" protein, myosin, it is opportune both to model the structural change in the hydrolytic transition, ATP (myosin-bound) + H2O --> ADP.Pi (myosin-bound) and to check the plausibility of the model by appropriate site-directed mutations in the functional system. Here, we made a series of mutations to investigate the role of the salt-bridge between Glu-470 and Arg-247 (of chicken smooth muscle myosin) that has been inferred from crystallography to be a central feature of the transition [Fisher, A. J., Smith, C. A., Thoden, J. B. , Smith, R., Sutoh, K., Holden, H. M., & Rayment, I. (1995) Biochemistry 34, 8960-8972]. Our results suggest that whether in the normal, or in the inverted, direction an intact salt-bridge is necessary for ATP hydrolysis, but when the salt-bridge is in the inverted direction it does not support actin activation. Normally, fluorescence changes result from adding nucleotides to myosin; these signals are reported by Trp-512 (of chicken smooth muscle myosin). Our results also suggest that structural impairments in the 470-247 region interfere with the transmission of these signals to the responsive Trp.
authors.affiliation: Department of Structural Analysis, National Cardiovascular Center Research Institute, Fujishiro-dai, Suita, Osaka 565-8565, Japan. honishi@ri.ncvc.go.jp
authors.forename: H
authors.initials: H
authors.lastname: Onishi
authors.forename: S
authors.initials: S
authors.lastname: Kojima
authors.forename: K
authors.initials: K
authors.lastname: Katoh
authors.forename: K
authors.initials: K
authors.lastname: Fujiwara
authors.forename: H M
authors.initials: HM
authors.lastname: Martinez
authors.forename: M F
authors.initials: MF
authors.lastname: Morales
mesh_terms: D000818:Animals; D002645:Chickens; D016297:Mutagenesis, Site-Directed; D015879:Myosin Subfragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D011487:Protein Conformation; D012492:Salts; D013329:Structure-Activity Relationship; D014364:Tryptophan / Q000737:chemistry* / Q000378:metabolism
chemical_list: D015879:Myosin Subfragments; D012492:Salts; D014364:Tryptophan