title: A flexible domain is essential for the large step size and processivity of myosin VI.
abstract: Myosin VI moves processively along actin with a larger step size than expected from the size of the motor. Here, we show that the proximal tail (the approximately 80-residue segment following the IQ domain) is not a rigid structure but, rather, a flexible domain that permits the heads to separate. With a GCN4 coiled coil inserted in the proximal tail, the heads are closer together in electron microscopy (EM) images, and the motor takes shorter processive steps. Single-headed myosin VI S1 constructs take nonprocessive 12 nm steps, suggesting that most of the processive step is covered by a diffusive search for an actin binding site. Based on these results, we present a mechanical model that describes stepping under an applied load.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Rock
authors.forename: Bhagavathi
authors.initials: B
authors.lastname: Ramamurthy
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Dunn
authors.forename: Sara
authors.initials: S
authors.lastname: Beccafico
authors.forename: Bhadresh R
authors.initials: BR
authors.lastname: Rami
authors.forename: Carl
authors.initials: C
authors.lastname: Morris
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Spink
authors.forename: Clara
authors.initials: C
authors.lastname: Franzini-Armstrong
authors.forename: James A
authors.initials: JA
authors.lastname: Spudich
authors.forename: H Lee
authors.initials: HL
authors.lastname: Sweeney
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008854:Microscopy, Electron; D024701:Myosin Type V / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013552:Swine
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D029701:Saccharomyces cerevisiae Proteins; C054562:yellow fluorescent protein, Bacteria; D011494:Protein Kinases; D024701:Myosin Type V