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Molecular cloning of the gene for the human placental GTP-binding protein Gp (G25K): identification of this GTP-binding protein as the human homolog of the yeast cell-division-cycle protein CDC42.

ABSTRACT: We have isolated cDNA clones from a human placental library that code for a low molecular weight GTP-binding protein originally designated Gp (also called G25K). This identification is based on comparisons with the available peptide sequences for the purified human Gp protein and the use of two highly specific anti-peptide antibodies. The predicted amino acid sequence of the protein is very similar to those of various members of the ras superfamily of low molecular weight GTP-binding proteins, including the N-, Ki-, and Ha-ras proteins (30-35% identical), the rho proteins (approximately 50% identical), and the rac proteins (approximately 70% identical). The highest degree of sequence identity (80%) is found with the Saccharomyces cerevisiae cell-division-cycle protein CDC42. The human placental gene, which we designate CDC42Hs, complements the cdc42-1 mutation in S. cerevisiae, which suggests that this GTP-binding protein is the human homolog of the yeast protein.

SUBMITTER: Shinjo K

PROVIDER: S-EPMC55272 | biostudies-other | 1990 Dec

REPOSITORIES: biostudies-other

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Molecular cloning of the gene for the human placental GTP-binding protein Gp (G25K): identification of this GTP-binding protein as the human homolog of the yeast cell-division-cycle protein CDC42.

Shinjo K K Koland J G JG Hart M J MJ Narasimhan V V Johnson D I DI Evans T T Cerione R A RA

Proceedings of the National Academy of Sciences of the United States of America 19901201 24

We have isolated cDNA clones from a human placental library that code for a low molecular weight GTP-binding protein originally designated Gp (also called G25K). This identification is based on comparisons with the available peptide sequences for the purified human Gp protein and the use of two highly specific anti-peptide antibodies. The predicted amino acid sequence of the protein is very similar to those of various members of the ras superfamily of low molecular weight GTP-binding proteins, i ...[more]

PMID: 2124704

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Project description:BackgroundAssembly of the tubulin-like GTPase, FtsZ, at the future division site initiates the process of bacterial cytokinesis. The FtsZ ring serves as a platform for assembly of the division machinery and constricts at the leading edge of the invaginating septum during cytokinesis. In vitro, FtsZ assembles in a GTP-dependent manner, forming straight filaments that curve upon GTP hydrolysis. FtsZ binds but cannot hydrolyze GTP as a monomer. Instead, the active site for GTP hydrolysis is formed at the monomer-monomer interface upon dimerization. While the dynamics of GTP hydrolysis and assembly have been extensively studied in vitro, significantly less is known about the role of GTP binding and hydrolysis in vivo. ftsZ84, a GTPase defective allele of Escherichia coli ftsZ, provides a striking example of the disconnect between in vivo and in vitro FtsZ assembly.ResultsAlthough ftsZ84 mutants are defective for FtsZ ring formation and division under nonpermissive conditions, they are near wild type for ring formation and division under permissive conditions. In vitro, however, purified FtsZ84 is defective in GTP binding, hydrolysis and assembly under standard reaction conditions. To clarify the nature of the FtsZ84 assembly defect, we isolated and characterized three intragenic suppressors of ftsZ84. All three suppressor mutations increased the apparent affinity of FtsZ84 for GTP, consistent with improved subunit-subunit interactions along the longitudinal interface. Although kinetic analysis indicates that the suppressor mutations increase the affinity of FtsZ84 for GTP, all three exhibit reduced rates of GTP hydrolysis and fail to support assembly in vitro.ConclusionTogether, our data suggest that FtsZ, and potentially other enzymes whose assembly is similarly regulated, can compensate for defects in catalysis through increases in substrate binding and subunit-subunit interactions. In addition, these results highlight the dichotomy between commonly used in vitro assembly conditions and FtsZ ring formation in the complex intracellular milieu.

Dataset Information

Molecular cloning of the gene for the human placental GTP-binding protein Gp (G25K): identification of this GTP-binding protein as the human homolog of the yeast cell-division-cycle protein CDC42.

Publications

Molecular cloning of the gene for the human placental GTP-binding protein Gp (G25K): identification of this GTP-binding protein as the human homolog of the yeast cell-division-cycle protein CDC42.

Similar Datasets

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