Taxonomic distribution of proteins containing PUR domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing PUR domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

The R3H motif: a domain that binds single-stranded nucleic acids.

Grishin NV
Trends Biochem Sci. 1998; 23: 329-30

Association of human Pur alpha with the retinoblastoma protein, Rb,regulates binding to the single-stranded DNA Pur alpha recognitionelement.

Johnson EM, Chen PL, Krachmarov CP, Barr SM, Kanovsky M, Ma ZW, Lee WH
J Biol Chem. 1995; 270: 24352-60

The retinoblastoma protein, Rb, is detected in extracts of monkey CV-1cells complexed with Pur alpha, a sequence-specific single-strandedDNA-binding protein implicated in control of gene transcription and DNAreplication. These complexes can be immunoextracted from cell lysatesusing monoclonal antibodies to either Pur alpha or Rb. The Pur alpha-Rbcomplexes contain a form of Pur alpha with extensive post-syntheticmodification, as demonstrated following expression of Pur alpha cDNA fusedto a 9-amino acid epitope tag. Human Pur alpha, expressed as a glutathioneS-transferase fusion protein, specifically binds to the hypophosphorylatedform of Rb with an affinity as high as that of SV40 large T-antigen. Inthe absence of DNA, glutathione S-transferase-Pur alpha binds to p56RB, anNH2-terminal-truncated Rb protein purified from Escherichia coli,containing the T-antigen binding domain, to form multimeric complexes. Thesingle-stranded DNA Pur alpha recognition element disrupts thesecomplexes. Conversely, high concentrations of p56RB prevent Pur alphabinding to DNA. Through use of a series of deletion mutants, the DNAbinding activity of Pur alpha is localized to a series of modular aminoacid repeats. Rb binding involves a Pur alpha region with limited homologyto the Rb-binding region of SV40 large T-antigen. Binding of Pur alpha top56RB, the COOH-terminal portion of Rb, is inhibited by a syntheticpeptide containing the T-antigen Rb-binding motif.

Sequence of cDNA comprising the human pur gene and sequence-specificsingle-stranded-DNA-binding properties of the encoded protein.

Bergemann AD, Ma ZW, Johnson EM
Mol Cell Biol. 1992; 12: 5673-82

The human Pur factor binds strongly to a sequence element repeated withinzones of initiation of DNA replication in several eukaryotic cells. Theprotein binds preferentially to the purine-rich single strand of thiselement, PUR. We report here the cloning and sequencing of a cDNA encodinga protein with strong affinity for the PUR element. Analysis with a seriesof mutated oligonucleotides defines a minimal single-stranded DNAPur-binding element. The expressed Pur open reading frame encodes aprotein of 322 amino acids. This protein, Pur alpha, contains threerepeats of a consensus motif of 23 amino acids and two repeats of a secondconsensus motif of 26 amino acids. Near its carboxy terminus, the proteinpossesses an amphipathic alpha-helix and a glutamine-rich domain. Therepeat region of Pur cDNA is homologous to multiple mRNA species in eachof several human cell lines and tissues. The HeLa cDNA library alsoincludes a clone encoding a related gene, Pur beta, containing a versionof the 23-amino-acid consensus motif similar, but not identical, to thosein Pur alpha. Results indicate a novel type of modular protein withcapacity to bind repeated elements in single-stranded DNA.