A conserved domain in the tail region of the Saccharomyces cerevisiae Na+/H+ antiporter (Nha1p) plays important roles in localization and salinity-resistant cell-growth.
The Saccharomyces cerevisiae Na(+)/H(+) antiporter Nha1p has a two-domain structure consisting of an N-terminal integral membrane region and a C-terminal cytoplasmic region. We previously identified six distinct cytoplasmic domains (C1-C6) conserved among yeast species and here we performed detailed structure-function analysis of the C1 domain (16 residues). Deletion of the C1 domain causes extensive inhibition of cell-growth under high salinity conditions. Mutants with single residue deletions or various amino acid substitutions affecting the C1 domain were analyzed with respect to salinity-dependent growth and Nha1p localization. The C1 domain was found to consist of two subdomains: (i) The first three N-proximal residues, which in conjunction with the integral membrane region play a crucial role in the targeting of Nha1p to the cytoplasmic membrane, and (ii) the portion between Leu-439 and Thr-449, which is not required for localization, but in which four residues (Gly-440, Arg-441, His-442, and Ile-446) affect salinity-sensitive cell-growth by possibly influencing the antiporter activity. Based on the overall similarity of the two-domain structure of Nha1p to that of mammalian Na(+)/H(+) antiporters, the functional importance of domains proximal to the membrane region is discussed.
Department of Biological Sciences, Graduate School of Science, Osaka University, 1-16 Machikaneyama-cho, Toyonaka City, Osaka 560-0043.
Keiji
K
Mitsui
Shinya
S
Kamauchi
Norihiro
N
Nakamura
Hiroki
H
Inoue
Hiroshi
H
Kanazawa
D000595:Amino Acid Sequence; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects*; D017124:Conserved Sequence; D025141:Drug Resistance, Fungal / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology*
D027682:Cation Transport Proteins; D008565:Membrane Proteins; C000631624:NHA1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride