title: The Globular Tail Domain of Myosin-5a Functions as a Dimer in Regulating the Motor Activity.
abstract: Myosin-5a contains two heavy chains, which are dimerized via the coiled-coil regions. Thus, myosin-5a comprises two heads and two globular tail domains (GTDs). The GTD is the inhibitory domain that binds to the head and inhibits its motor function. Although the two-headed structure is essential for the processive movement of myosin-5a along actin filaments, little is known about the role of GTD dimerization. Here, we investigated the effect of GTD dimerization on its inhibitory activity. We found that the potent inhibitory activity of the GTD is dependent on its dimerization by the preceding coiled-coil regions, indicating synergistic interactions between the two GTDs and the two heads of myosin-5a. Moreover, we found that alanine mutations of the two conserved basic residues at N-terminal extension of the GTD not only weaken the inhibitory activity of the GTD but also enhance the activation of myosin-5a by its cargo-binding protein melanophilin (Mlph). These results are consistent with the GTD forming a head to head dimer, in which the N-terminal extension of the GTD interacts with the Mlph-binding site in the counterpart GTD. The Mlph-binding site at the GTD-GTD interface must be exposed prior to the binding of Mlph. We therefore propose that the inhibited Myo5a is equilibrated between the folded state, in which the Mlph-binding site is buried, and the preactivated state, in which the Mlph-binding site is exposed, and that Mlph is able to bind to the Myo5a in preactivated state and activates its motor function.
authors.affiliation: From the Group of Cell Motility and Muscle Contraction, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China and the University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Wen-Bo
authors.initials: WB
authors.lastname: Zhang
authors.affiliation: From the Group of Cell Motility and Muscle Contraction, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China and.
authors.forename: Lin-Lin
authors.initials: LL
authors.lastname: Yao
authors.affiliation: From the Group of Cell Motility and Muscle Contraction, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China and lixd@ioz.ac.cn.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Li
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D006153:Guanosine Diphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024701:Myosin Type V / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000072417:Protein Domains; D017510:Protein Folding; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C492410:MLPH protein, human; D006153:Guanosine Diphosphate; C077511:MYO5A protein, human; D006160:Guanosine Triphosphate; D024701:Myosin Type V; D018995:Myosin Heavy Chains
keywords: allosteric regulation; cytoskeleton; intracellular trafficking; molecular motor; myosin; myosin-5a