title: Mutation in the SH1 helix reduces the activation energy of the ATP-induced conformational transition of myosin.
abstract: The SH1 helix is a joint that links the converter subdomain to the rest of the myosin motor domain. Recently, we showed that a mutation within the SH1 helix in Dictyostelium myosin II (R689H) reduced the elasticity and thermal stability of the protein. To reveal the involvement of the SH1 helix in ATP-dependent conformational changes of the motor domain, we have investigated the effects of the R689H mutation on the conformational changes of the converter, using a GFP-based fluorescence resonance energy transfer method. Although the mutation does not seem to strongly affect conformations, we found that it significantly reduced the activation energy required for the ATP-induced conformational transition corresponding to the recovery stroke. Given the effects of the mutation on the mechanical properties of myosin, we propose that the SH1 helix plays an important role in the mechanochemical energy conversion underlying the conformational change of the myosin motor domain.
authors.affiliation: Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550, Japan. iwai-sosuke@aist.go.jp
authors.forename: Sosuke
authors.initials: S
authors.lastname: Iwai
authors.forename: Shigeru
authors.initials: S
authors.lastname: Chaen
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D004735:Energy Transfer; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D016297:Mutagenesis, Site-Directed; D009218:Myosins / Q000737:chemistry* / Q000648:ultrastructure*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D018909:src Homology Domains
chemical_list: D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D009218:Myosins