title: Isoform-specific complementation of the yeast sac6 null mutation by human fimbrin.
abstract: The actin cytoskeleton is a fundamental component of eukaryotic cells, with both structural and motile roles. Actin and many of the actin-binding proteins found in different cell types are highly conserved, showing considerable similarity in both primary structure and biochemical properties. To make detailed comparisons between homologous proteins, it is necessary to know whether the various proteins are functionally, as well as structurally, conserved. Fimbrin is an example of a cytoskeletal component that, as shown by sequence determinations and biochemical characterizations, is conserved between organisms as diverse as Saccharomyces cerevisiae and humans. In this study, we examined whether the human homolog can substitute for the yeast protein in vivo. We report here that two isoforms of human fimbrin, also referred to as T- and L-plastin, can both substitute in vivo for yeast fimbrin, also known as Sac6p, whereas a third isoform, I-fimbrin (or I-plastin), cannot. We demonstrate that the human T- and L-fimbrins, in addition to complementing the temperature-sensitive growth defect of the sac6 null mutant, restore both normal cytoskeletal organization and cell shape to the mutant cells. In addition, we show that human T- and L-fimbrins can complement a sporulation defect caused by the sac6 null mutation. These findings indicate that there is a high degree of functional conservation in the cytoskeleton, even between organisms as diverse as S. cerevisiae and humans.
authors.affiliation: Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721.
authors.forename: A E
authors.initials: AE
authors.lastname: Adams
authors.forename: W
authors.initials: W
authors.lastname: Shen
authors.forename: C S
authors.initials: CS
authors.lastname: Lin
authors.forename: J
authors.initials: J
authors.lastname: Leavitt
authors.forename: P
authors.initials: P
authors.lastname: Matsudaira
mesh_terms: D000818:Animals; D001483:Base Sequence; D048429:Cell Size; D002645:Chickens; D003599:Cytoskeleton / Q000648:ultrastructure; D017931:DNA Primers / Q000737:chemistry; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D006801:Humans; D008562:Membrane Glycoproteins / Q000145:classification / Q000502:physiology*; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D013172:Spores, Fungal
chemical_list: D017931:DNA Primers; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C026742:plastin