title: RAP kinase, a new enzyme phosphorylating the acidic P proteins from Saccharomyces cerevisiae.
abstract: A new protein kinase, showing a high specificity for the ribosomal acidic P proteins (RAP kinase) has been purified and characterized from Saccharomyces cerevisiae extracts. Purification was carried out by four chromatographic steps, including DEAE-cellulose, phosphocellulose, heparin-Sepharose and P protein-Sepharose. The purified enzyme preparation contains only one polypeptide of around 55 kDa as determined by SDS gel electrophoresis and gradient centrifugation. RAP kinase is different from all previous well-characterized kinases and does not show cross-reaction with antibodies to the 71 kDa 60S ribosomal subunit-specific kinase PK60 previously reported. The enzyme uses ATP as a better phosphate donor and is less sensitive to heparin than casein kinase II but is moderately affected by salt. Among the different substrates tested, ribosomal acidic proteins are preferentially modified by RAP kinase, which phosphorylates only serine residues in the four P proteins as well as the related ribosomal protein P0. Casein is phosphorylated at a much lower level. All the data indicate that RAP kinase might be the enzyme responsible for the phosphorylation of the P proteins, and in this way may also participate in a possible translational regulatory mechanism.
authors.affiliation: Centro de Biologia Molecular, UAM, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Szyszka
authors.forename: G
authors.initials: G
authors.lastname: Bou
authors.forename: J P
authors.initials: JP
authors.lastname: Ballesta
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D015153:Blotting, Western; D002845:Chromatography; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D005656:Fungal Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D008970:Molecular Weight; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D015800:Protozoan Proteins; D012269:Ribosomal Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; C064601:L12E protein, Trypanosoma cruzi; D047428:Protein Kinase Inhibitors; D015800:Protozoan Proteins; D012269:Ribosomal Proteins; D010768:Phosphoserine; D000255:Adenosine Triphosphate; D006493:Heparin; D011494:Protein Kinases; C099264:RAP kinase