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S A Fedorov

Publications and source records attributed to S A Fedorov.

9 recordsLinked to original sources
PubMed2000

PR48, a novel regulatory subunit of protein phosphatase 2A, interacts with Cdc6 and modulates DNA replication in human cells.

Initiation of DNA replication in eukaryotes is dependent on the activity of protein phosphatase 2A (PP2A), but specific phosphoprotein substrates pertinent to this requirement have not been identified. A novel regulatory subunit of PP2A, termed PR48, was identified by a yeast two-hybrid screen of a human placental cDNA library, using human Cdc6, an essential component of prereplicative complexes, as bait. PR48 binds specifically to an amino-terminal segment of Cdc6 and forms functional holoenzyme complexes with A and C subunits of PP2A. PR48 localizes to the nucleus of mammalian cells, and its forced overexpression perturbs cell cycle progression, causing a G(1) arrest. These results suggest that dephosphorylation of Cdc6 by PP2A, mediated by a specific interaction with PR48, is a regulatory event controlling initiation of DNA replication in mammalian cells.

Amino Acid Sequence↗
PubMed1998

Identification of structural elements involved in the interaction of simian virus 40 small tumor antigen with protein phosphatase 2A.

SV40 small tumor antigen (small-t) was used as a model to identify structural elements involved in the interactions between regulatory proteins and protein phosphatase 2A (PP2A). Using mutant proteins and synthetic peptides, we identified a small domain within small-t that is a major site for interaction with the dimeric form of PP2A. A series of small-t truncation mutants identified a region surrounding the first of two conserved cysteine clusters that was critical for interaction with PP2A. These mutants also identified additional regions of small-t that contribute to high affinity interaction. Deletion of residues 110-119, which encompass the first cysteine cluster, resulted in a protein that failed to bind to PP2A. Synthetic peptides that contained residues 105-122 of small-t blocked binding of small-t to PP2A. These peptides also inhibited the phosphatase activity of PP2A in a manner analogous to full-length small-t. The active small-t peptides adopt a beta-strand structure that was essential for high affinity interaction with the PP2A dimer. Based on circular dichroism measurements, the same cysteine cluster-containing peptides that bind to PP2A also interact with zinc. Interaction with zinc required the conserved cysteines but was not required for interaction with PP2A.

Amino Acid Sequence↗
PubMed1984

Effect of Zajdela ascites hepatoma on the activity and synthesis of liver histidase of tumor-bearing rats.

The synthesis of histidase occurs only in free polyribosomes. The relative content of histidase synthesizing polyribosomes in rat liver, in Zajdela ascites hepatoma cells and in the liver of tumor-bearing rats is equal to 1.35%, 0.11% and 0.57%, respectively (of the total amount of free polyribosomes). It was found that hepatoma cell sap has an inhibitory effect on the synthesis of proteins in the cell-free system reconstructed from polyribosomes and cell sap of control rats.

Ammonia-Lyases↗
PubMedDate not supplied

[Enzymatic conversion of L-histidine to urocanic acid using immobilized histidase from the rat liver].

A procedure is described for immobilization of partially purified histidase by means of covalent binding of the enzyme with amino ethyl cellulose activated by glutaraldehyde. The preparation obtained was stable within 6 months at 5 degrees and within 40 days at 39 degrees. The preparation of immobilized histidase might be used for enzymatic synthesis of urocanic acid from histidine.

Acrylic Resins↗