title: A novel membrane protein capable of binding the Na+/H+ antiporter (Nha1p) enhances the salinity-resistant cell growth of Saccharomyces cerevisiae.
abstract: The Na+/H+ antiporter Nha1p of Saccharomyces cerevisiae plays an important role in maintaining intracellular pH and Na+ homeostasis. Nha1p has a two-domain structure composed of integral membrane and hydrophilic tail regions. Overexpression of a peptide of approximately 40 residues (C1+C2 domains) that is localized in the juxtamembrane area of its cytoplasmic tail caused cell growth retardation in highly saline conditions, possibly by decreasing Na+/H+ antiporter activity. A multicopy suppressor gene of this growth retardation was identified from a yeast genome library. The clone encodes a novel membrane protein denoted as COS3 in the genome data base. Overexpression or deletion of COS3 increases or decreases salinity-resistant cell growth, respectively. However, in nha1Delta cells, overexpression of COS3 alone did not suppress the growth retardation. Cos3p and a hydrophilic portion of Cos3p interact with the C1+C2 peptide in vitro, and Cos3p is co-precipitated with Nha1p from yeast cell extracts. Cos3p-GFP mainly resides at the vacuole, but overexpression of Nha1p caused a portion of the Cos3p-GFP proteins to shift to the cytoplasmic membrane. These observations suggest that Cos3p is a novel membrane protein that can enhance salinity-resistant cell growth by interacting with the C1+C2 domain of Nha1p and thereby possibly activating the antiporter activity of this protein.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, Osaka University, Machikaneyama-cho 1-16, Toynaka City, Osaka 560-0043, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Mitsui
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Ochi
authors.forename: Norihiro
authors.initials: N
authors.lastname: Nakamura
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Doi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Inoue
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kanazawa
mesh_terms: D000595:Amino Acid Sequence; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015723:Gene Library; D005799:Genes, Dominant; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry* / Q000378:metabolism*; D013347:Subcellular Fractions; D013997:Time Factors
chemical_list: C484692:COS3 protein, S cerevisiae; D027682:Cation Transport Proteins; D017931:DNA Primers; D008164:Luminescent Proteins; D008565:Membrane Proteins; C000631624:NHA1 protein, S cerevisiae; D010455:Peptides; D029701:Saccharomyces cerevisiae Proteins; D017923:Sodium-Hydrogen Exchangers; D049452:Green Fluorescent Proteins; D012965:Sodium Chloride