title: Organelle targeting of myosin XI is mediated by two globular tail subdomains with separate cargo binding sites.
abstract: Myosin XI are actin-based molecular motors that are thought to drive organelle movements in plants, analogous to myosin V in animals and fungi. Similar domain structure of these myosins suggests that binding to organelles may occur via the globular tail domain in both types of motors, even though sequence similarity is low. To address this hypothesis, we developed a structure homology model for the globular tail of MYA1, a myosin XI from Arabidopsis, based on the known structure of yeast myosin V (Myo2p) globular tail. This model suggested an interaction between two subdomains of the globular tail which was verified by yeast two-hybrid assay and by in vivo bimolecular fluorescence complementation (BiFC). Interface mapping demonstrated that this subdomain interaction depends critically on the C terminus of helix H6 as well as three specific residues in helices H3 and H15, consistent with the structural prediction. The reconstituted globular tails of several Arabidopsis myosin XIs in BiFC assays targeted to peroxisomes in plant cells, identifying this domain as sufficient for cargo binding. Unlike myosin V, either subdomain of myosin XI alone was targeting-competent and responsible for association with different organelles. In addition, our data suggest that organelle binding is regulated by an allosteric interaction between two tail subdomains. We conclude that the globular tail of myosin XI shares a similar structure with that of myosin V, but has evolved plant-specific cargo binding mechanisms.
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Li
authors.forename: Andreas
authors.initials: A
authors.lastname: Nebenführ
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D001693:Biological Transport, Active / Q000502:physiology; D005816:Genetic Complementation Test; D008958:Models, Molecular; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D024701:Myosin Type V / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009218:Myosins / Q000737:chemistry* / Q000378:metabolism; D015388:Organelles / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D040681:Structural Homology, Protein; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C087819:MYA1 protein, Arabidopsis; C077512:MYO2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D009218:Myosins