title: A structural model for phosphorylation control of Dictyostelium myosin II thick filament assembly.
abstract: Myosin II thick filament assembly in Dictyostelium is regulated by phosphorylation at three threonines in the tail region of the molecule. Converting these three threonines to aspartates (3 x Asp myosin II), which mimics the phosphorylated state, inhibits filament assembly in vitro, and 3 x Asp myosin II fails to rescue myosin II-null phenotypes. Here we report a suppressor screen of Dictyostelium myosin II-null cells containing 3 x Asp myosin II, which reveals a 21-kD region in the tail that is critical for the phosphorylation control. These data, combined with new structural evidence from electron microscopy and sequence analyses, provide evidence that thick filament assembly control involves the folding of myosin II into a bent monomer, which is unable to incorporate into thick filaments. The data are consistent with a structural model for the bent monomer in which two specific regions of the tail interact to form an antiparallel tetrameric coiled-coil structure.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307, USA.
authors.forename: W
authors.initials: W
authors.lastname: Liang
authors.forename: H M
authors.initials: HM
authors.lastname: Warrick
authors.forename: J A
authors.initials: JA
authors.lastname: Spudich
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D000409:Alanine / Q000378:metabolism; D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D016054:DNA, Protozoan / Q000187:drug effects / Q000528:radiation effects; D004023:Dictyostelium / Q000166:cytology* / Q000378:metabolism*; D006912:Hydroxyquinolines / Q000494:pharmacology; D008854:Microscopy, Electron; D008954:Models, Biological; D016296:Mutagenesis; D009218:Myosins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000187:drug effects / Q000528:radiation effects; D013489:Suppression, Genetic
chemical_list: D016054:DNA, Protozoan; D006912:Hydroxyquinolines; D010455:Peptides; D015800:Protozoan Proteins; D001224:Aspartic Acid; C010494:nonyl-4-hydroxyquinoline-N-oxide; D009218:Myosins; D000409:Alanine