title: Identification of the Isoform-specific Interactions between the Tail and the Head of Class V Myosin.
abstract: Vertebrates have three isoforms of class V myosin (Myo5), Myo5a, Myo5b, and Myo5c, which are involved in transport of multiple cargoes. It is well established that the motor functions of Myo5a and Myo5b are regulated by a tail inhibition mechanism. Here we found that the motor function of Myo5c was also inhibited by its globular tail domain (GTD), and this inhibition was abolished by high Ca(2+), indicating that the tail inhibition mechanism is conserved in vertebrate Myo5. Interestingly, we found that Myo5a-GTD and Myo5c-GTD were not interchangeable in terms of inhibition of motor function, indicating isoform-specific interactions between the GTD and the head of Myo5. To identify the isoform-specific interactions, we produced a number of Myo5 chimeras by swapping the corresponding regions of Myo5a and Myo5c. We found that Myo5a-GTD, with its H11-H12 loop being substituted with that of Myo5c, was able to inhibit the ATPase activity of Myo5c and that Myo5a-GTD was able to inhibit the ATPase activity of Myo5c-S1 and Myo5c-HMM only when their IQ1 motif was substituted with that of Myo5a. Those results indicate that the H11-H12 loop in the GTD and the IQ1 motif in the head dictate the isoform-specific interactions between the GTD and head of Myo5. Because the IQ1 motif is wrapped by calmodulin, whose conformation is influenced by the sequence of the IQ1 motif, we proposed that the calmodulin bound to the IQ1 motif interacts with the H11-H12 loop of the GTD in the inhibited state of Myo5.
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.
authors.forename: Mei
authors.initials: M
authors.lastname: Shen
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: Zekuan
authors.initials: Z
authors.lastname: Lu
authors.affiliation: the Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler, Texas 75708.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ikebe
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: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism*; D024701:Myosin Type V / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D060066:Protein Interaction Maps; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: C459104:MYO5C protein, human; C513082:Myo5a protein, mouse; D020033:Protein Isoforms; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D002118:Calcium
keywords: ATPase; allosteric regulation; intracellular trafficking; molecular motor; myosin; unconventional myosin