A Sec7-related protein in Paramecium

Saraswathy Nair, Charles Guerra, Peter Satir

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We have cloned and sequenced a SEC7-related gene in Paramecium tetraurelia that contains an open reading frame for 1135 amino acids encoding a 133 kDa protein, PSec7. Sec7, first identified in vesicular trafficking mutants in yeast, and its phylogenetic homologues function as guanine- nucleotide exchange factors for small G-proteins such as ARF (ADP- ribosylation factor). The deduced amino acid sequence in PSec7 for the motifs that form the ARF binding site are more than 70% identical to yeast Sec7 and similarly identical to ARNO, the human ARF exchange factor, with correct positioning of the critical glutamic acid residue within the motif region. Overall, the identity of PSec7 to yeast Sec7 is 32%. The deduced amino acid sequence also has five sequences that resemble IQ motifs, EF hand binding domains found in all myosins, and two pleckstrin homology domains. Similar sequences are present in yeast Sec7 and other Sec7-related molecules. A protein kinase A phosphorylation site may also be present. Southern blots suggest that a single gene encodes PSec7. Northern blots show that the message encoding PSec7 is induced on deciliation, followed by ciliogenesis, which suggests a role for PSec7 in cilia such as transport or targeting of ciliary membrane components.

Original languageEnglish (US)
Pages (from-to)1249-1257
Number of pages9
JournalFASEB Journal
Issue number10
StatePublished - 1999
Externally publishedYes


  • Cilia
  • GEF
  • Guanine nucleotide exchange factor
  • IQ motifs

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics


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