title: Functional adaptation between yeast actin and its cognate myosin motors.
abstract: We employed budding yeast and skeletal muscle actin to examine the contribution of the actin isoform to myosin motor function. While yeast and muscle actin are highly homologous, they exhibit different charge density at their N termini (a proposed myosin-binding interface). Muscle myosin-II actin-activated ATPase activity is significantly higher with muscle versus yeast actin. Whether this reflects inefficiency in the ability of yeast actin to activate myosin is not known. Here we optimized the isolation of two yeast myosins to assess actin function in a homogenous system. Yeast myosin-II (Myo1p) and myosin-V (Myo2p) accommodate the reduced N-terminal charge density of yeast actin, showing greater activity with yeast over muscle actin. Increasing the number of negative charges at the N terminus of yeast actin from two to four (as in muscle) had little effect on yeast myosin activity, while other substitutions of charged residues at the myosin interface of yeast actin reduced activity. Thus, yeast actin functions most effectively with its native myosins, which in part relies on associations mediated by its outer domain. Compared with yeast myosin-II and myosin-V, muscle myosin-II activity was very sensitive to salt. Collectively, our findings suggest differing degrees of reliance on electrostatic interactions during weak actomyosin binding in yeast versus muscle. Our study also highlights the importance of native actin isoforms when considering the function of myosins.
authors.affiliation: Department of Molecular Physiology & Biophysics, University of Vermont, Burlington, Vermont 05405.
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Stark
authors.affiliation: Department of Biochemistry, University of Iowa College of Medicine, Iowa City, Iowa 52242.
authors.forename: Kuo-Kuang
authors.initials: KK
authors.lastname: Wen
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.
authors.forename: John S
authors.initials: JS
authors.lastname: Allingham
authors.affiliation: Department of Biochemistry, University of Iowa College of Medicine, Iowa City, Iowa 52242.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Rubenstein
authors.affiliation: Department of Molecular Physiology & Biophysics, University of Vermont, Burlington, Vermont 05405. Electronic address: matthew.lord@uvm.edu.
authors.forename: Matthew
authors.initials: M
authors.lastname: Lord
mesh_terms: D000199:Actins / Q000737:chemistry*; D000205:Actomyosin / Q000737:chemistry; D000595:Amino Acid Sequence; D004023:Dictyostelium / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D024461:Myosin Type I / Q000737:chemistry* / Q000378:metabolism; D024462:Myosin Type II / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D055672:Static Electricity
chemical_list: D000199:Actins; D020033:Protein Isoforms; D000205:Actomyosin; D024461:Myosin Type I; D024462:Myosin Type II