An actin monomer binding activity localizes to the carboxyl-terminal half of the Saccharomyces cerevisiae cyclase-associated protein.

The Saccharomyces cerevisiae adenylyl cyclase complex contains at least two subunits, a 200-kDa catalytic subunit and a 70-kDa cyclase-associated protein, CAP (also called Srv2p). Genetic studies suggested two roles for CAP, one as a positive regulator of cAMP levels in yeast and a second role as a cytoskeletal regulator. We ...
present evidence showing that CAP sequesters monomeric actin (Kd in the range of 0.5-5 microM), decreasing actin incorporation into actin filaments. Anti-CAP monoclonal antibodies co-immunoprecipitate a protein with a molecular size of about 46 kDa. When CAP was purified from yeast using an anti-CAP monoclonal antibody column, the 46-kDa protein co-purified with a stoichiometry of about 1:1 with CAP. Western blots identified the 46-kDa protein as yeast actin. CAP also bound to muscle actin in vitro in immunoprecipitation assays and falling ball viscometry assays. Experiments with pyrene-labeled actin demonstrated that CAP sequesters actin monomers. The actin monomer binding activity is localized to the carboxyl-terminal half of CAP. Together, these data suggest that yeast CAP regulates the yeast cytoskeleton by sequestering actin monomers.
Mesh Terms:
Actins, Adaptor Proteins, Signal Transducing, Adenylate Cyclase, Animals, Antibodies, Monoclonal, Binding Sites, Cell Cycle Proteins, Chromatography, Affinity, Cytoskeletal Proteins, Drosophila Proteins, Electrophoresis, Polyacrylamide Gel, Fungal Proteins, Kinetics, Macromolecular Substances, Microfilament Proteins, Muscles, Protein Binding, Rabbits, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Species Specificity, Sulfur Radioisotopes, Viscosity
J. Biol. Chem.
Date: Mar. 10, 1995
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