title: A molecular evolution approach to study the roles of tropomyosin in fission yeast.
abstract: Tropomyosin, a coiled-coil protein that binds along the length of the actin filament, is a universal regulator of the actin cytoskeleton. We have taken a bioinformatics/proteomic approach to studying structure-function relationships in this protein. The presence of a single, essential tropomyosin gene, cdc8, in fission yeast, Schizosaccharomyces pombe, enables a systems-based approach to define the residues that are important for cellular functions. Using molecular evolution methodologies we identified the most conserved residues and related them to the coiled coil structure. Mutants in which one or more of 21 of the most conserved surface residues was mutated to Ala were tested for the ability to rescue growth of a temperature-sensitive cdc8 mutant when overexpressed at the restrictive temperature. Based on altered morphology of the septum and actin cytoskeleton, we selected three sets of mutations for construction of mutant cdc8 strains using marker reconstitution mutagenesis and analysis of recombinant protein in vitro: D16A.K30A, V114S.E117A.H118A and R121A.D131A.E138A. The mutations have sequence-specific effects on cellular morphology including cell length, organization of cytoskeletal structures (actin patches, actin cables and contractile rings), and in vitro actin affinity, lending credence to the proteomic approach introduced here. We propose that bioinformatics is a valid analysis tool for defining structure-function relationships in conserved proteins in this model organism.
authors.affiliation: Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, Piscataway, New Jersey, United States of America.
authors.forename: Susanne
authors.initials: S
authors.lastname: Cranz-Mileva
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Pamula
authors.forename: Bipasha
authors.initials: B
authors.lastname: Barua
authors.forename: Brinda
authors.initials: B
authors.lastname: Desai
authors.forename: Yaejee Hannah
authors.initials: YH
authors.lastname: Hong
authors.forename: Jacquelyn
authors.initials: J
authors.lastname: Russell
authors.forename: Richard
authors.initials: R
authors.lastname: Trent
authors.forename: Jianqiu
authors.initials: J
authors.lastname: Wang
authors.forename: Nancy C
authors.initials: NC
authors.lastname: Walworth
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Hitchcock-DeGregori
mesh_terms: D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D016296:Mutagenesis; D009154:Mutation; D017433:Protein Structure, Secondary; D012568:Schizosaccharomyces / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014335:Tropomyosin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C410737:Cdc8 protein, S pombe; D018797:Cell Cycle Proteins; D029702:Schizosaccharomyces pombe Proteins; D014335:Tropomyosin