title: Evidence against essential roles for subdomain 1 of actin in actomyosin sliding movements.
abstract: We have engineered acto-S1chimera proteins carrying the entire actin inserted in loop 2 of the motor domain of Dictyostelium myosin II with 24 or 18 residue-linkers (CP24 and CP18, respectively). These proteins were capable of self-polymerization as well as copolymerization with skeletal actin and exhibited rigor-like structures. The MgATPase rate of CP24-skeletal actin copolymer was 1.06 s(-1), which is slightly less than the V(max) of Dictyostelium S1. Homopolymer filaments of skeletal actin, CP24, and CP18 moved at 4.7+/-0.6, 2.9+/-0.6, and 4.1+/-0.8 microm/s (mean+/-SD), respectively, on coverslips coated with skeletal myosin at 27 degrees C. Statistically thermodynamic considerations suggest that the S1 portion of chimera protein mostly resides on subdomain 1 (SD-1) of the actin portion even in the presence of ATP. This and the fact that filaments of CP18 with shorter linkers moved faster than CP24 filaments suggest that SD-1 might not be as essential as conventionally presumed for actomyosin sliding interactions.
authors.affiliation: Department of Materials Processing, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579, Japan.
authors.forename: Md Shahjahan P
authors.initials: MS
authors.lastname: Siddique
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Eisaku
authors.initials: E
authors.lastname: Katayama
authors.forename: Taro Q P
authors.initials: TQ
authors.lastname: Uyeda
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*; D000205:Actomyosin / Q000737:chemistry* / Q000648:ultrastructure*; D000818:Animals; D001665:Binding Sites; D004023:Dictyostelium / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000737:chemistry*; D009038:Motion; D046912:Multiprotein Complexes / Q000737:chemistry / Q000648:ultrastructure; D024462:Myosin Type II / Q000737:chemistry* / Q000648:ultrastructure*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000648:ultrastructure; D013329:Structure-Activity Relationship
chemical_list: D000199:Actins; D020409:Molecular Motor Proteins; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; D000205:Actomyosin; D024462:Myosin Type II