Ras supergene family
Small GTP-binding protein
Restriction fragment length polymorphism
Springer Online Journal Archives 1860-2000
Summary Small GTP-binding proteins are encoded by ras-like genes and play a central role in cell differentiation and membrane vesicle transport. By screening genomic and cDNA libraries of the Ascomycete fungus Neurospora crassa with Zmypt genes from Zea mays we have isolated a member of the ypt gene family, Ncypt1. The gene resides on a 4 kb fragment of genomic DNA and contains four introns, which interrupt the coding sequence of a protein of 203 amino acid residues. The Ncytp1 gene was assigned to a single-copy gene encoding a transcript of 1.5 kb and a protein of 26 000 daltons. The gene maps on linkage group IIR between DB0001 and ccg-2 close to the Fsr-3 locus. Analysis of the nucleotide sequence and the deduced protein sequence revealed a striking homology to yeast, mouse and human genes encoding small GTP-binding proteins that are related to the ras supergene family. Homology was most significant to yptl from Schizosaccharomyces pombe, Mus musculus and Homo sapiens sharing 84.8%, 82.3%, and 82.3% identity, respectively. Common domains present in other small GTP-binding proteins were identified in the predicted sequence of the NCYPTI protein, and the arrangement of peptide motifs sharing similarity with well characterized, small GTP-binding proteins suggests that the NCYPT 1 protein is a GTPase. The C-terminal region extending from amino acid residues 175 to 199 shares only weak amino acid sequence similarity with other eukaryotic GTPases. Like other RAS proteins the NCYPTI protein contains two conserved C-terminal cysteine residues, suggesting post-translational modification(s) by fatty acylation required for membrane anchoring. The high degree of homology between the NCYPT 1 protein and eukaryotic YPT proteins suggests that NCYPTI could be involved in the control of secretory processes.
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