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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A salt-extraction procedure was used to isolate a nucleolar nonhistone protein fraction, containing [32P]phosphoserine, from the nucleoli of Novikoff hepatoma ascites cells. These proteins are similar in amino-acid composition to whole nuclear (chromosomal) nonhistone proteins. DNA-cellulose column chromatography showed that this fraction contains DNA-binding phosphoproteins, some of which will bind only to homologous (Novikoff) nucleolar or nuclear DNA.
Mol Cell Biochem 1976 Jan 31
PMID:DNA-cellulose column chromatography of phosphorylated nucleolar nonhistone proteins. 17 59

Chemical and enzymatic properties of four collagenases newly isolated from anaerobic Clostridium histolyticum, aerobic Achromobacter iophagus, and from two lower eucaryotes, the fungus Entomophthora coronata and the insect Hypoderma lineatum are reviewed. The problems of their biosynthesis and precursors, namely the effect of induction of collagenase and neutral proteinase in Achromobacter by their macromolecular substrates are discussed. The two bacterial collagenases are Zn-metallo-enzymes; the highly purified Clostridium collagenase contains cyst(e)ine, serine phosphate and tryptophan additionally to amino acids reported previously. Achromobacter collagenase has the highest specific activity of all collagenases; it yields by autolysis enzymatically active degraded forms. The active dimer is composed of two identical subunits of molecular weight 35,000. Similarities between Achromobacter collagenase, thermolysin and Bacillus subtilis neutral proteinase in molecular weight, amino acid composition, and amino acids important for the active sites are discussed. The two collagenases from low eucaryotes are serine proteinases; Hypoderma collagenase is homologous to the trypsin family in the amino terminal sequence. The initial cleavage of native collagen by highly purified bacterial collagenases occurs in the central helical part of the alpha chains and not progressively from the amino terminal end. One of the two initial cleavages produced by Achromobacter collagenase is situated in the region cleaved specifically by vertebrate collagenases, but with different bond specificity. The same is true for the insect collagenase. Entomophthora collagenase is a proteinase of broad specificity which also cleaves collagen in its helical parts. All four collagenases also degrade other proteins according to their bond specificity.
Mol Cell Biochem 1979 Jan 26
PMID:Some newly characterized collagenases from procaryotes and lower eucaryotes. 22 May 20

Ribosomal proteins of the dimorphic fungus Mucor racemosus were isolated and characterized by 2-dimensional gel electrophoresis. Proteins from ribosomes of the yeast and mycelial phase were compared, and were found to be qualitatively indistinguishable. The only consistent difference in the patterns of proteins was in a protein of the 40S subunit, S-6. This protein was phosphorylated in yeast and hyphae forms, but not in asexual sporangiospores. Studies on protein S-6 showed that it contained 3 phosphate residues per molecule of protein when maximally phosphorylated. In this form 3 different tryptic peptides were shown to contain a single phosphoserine. The S-6 protein also existed in forms containing 1 or 2 phosphates per molecule, depending on growth conditions.
Mol Gen Genet 1979 Aug
PMID:Ribosomal proteins of the dimorphic fungus, Mucor racemosus. 29 24

The catalytic subunit of protein phosphatase 2A (PP2Ac) stimulates the initiation of replication of simian virus 40 DNA in vitro by dephosphorylating T antigen at specific phosphoserine residues (K. H. Scheidtmann, D. M. Virshup, and T. J. Kelly, J. Virol. 65:2098-2101, 1991). To better define the biochemical mechanism responsible for this stimulation, we investigated the effect of PP2Ac on the interaction of T antigen with wild-type and mutant origins of replication. Analysis of the binding of T antigen to the wild-type origin as a function of protein concentration revealed that binding occurs in two relatively discrete steps: the assembly of a T-antigen hexamer on one half-site of the origin, followed by the assembly of the second hexamer on the other half-site. The major effect of PP2Ac was to stimulate binding of the second hexamer, so that the binding reaction became much more cooperative. This observation suggests that dephosphorylation of T antigen by PP2Ac primarily affects interactions between the two hexamers bound to the origin. Pretreatment with PP2Ac increased the ability of the bound T antigen to unwind the origin of replication but had no effect on the intrinsic helicase activity of the protein. Thus, dephosphorylation of PP2Ac appears to increase the efficiency of the initial opening of the origin by T antigen. An insertion mutation at the dyad axis in the simian virus 40 origin, which altered the structural relationship of the two halves of the origin, abolished the effect of the phosphatase on the cooperativity of binding and completely prevented origin unwinding. These findings suggest that the ability of T antigen to open the viral origin of DNA replication is critically dependent on the appropriate functional interactions between T-antigen hexamers and that these interactions are regulated by the phosphorylation state of the viral initiator protein.
Mol Cell Biol 1992 Nov
PMID:Mechanism of activation of simian virus 40 DNA replication by protein phosphatase 2A. 132 66

Using the synthetic peptide substrate Kemptide and cytosolic extracts of mouse fibroblasts transfected with a human insulin receptor cDNA construct, we have studied an insulin-sensitive serine kinase activity. This activity is rapidly stimulated by insulin (maximum within 5 min) and also by orthovanadate. During cell extract preparation, para-nitrophenylphosphate and phosphotyrosine are able to preserve the enzyme activity, while phosphothreonine and phosphoserine fail to do so. Using antiphosphotyrosine antibodies, specific immunoprecipitation of this insulin- and orthovanadate-sensitive serine kinase was obtained. We then analysed by gel filtration chromatography eluates containing tyrosine-phosphorylated proteins obtained from unstimulated, insulin- and vanadate-treated cells. We found that several activities, with molecular weights estimated to be 30 kDa and smaller, are stimulated by both, insulin and orthovanadate. As a whole, our data indicate that insulin and orthovanadate enhance the cytosolic content in at least 2 or 3 phosphotyrosine-containing serine kinase activities.
Mol Cell Biochem 1992 Feb 12
PMID:Insulin and orthovanadate stimulate multiple phosphotyrosine-containing serine kinases. 137 74

We report here the isolation and identification of the RNA specifically immunoprecipitated and covalently linked to the tumor suppressor gene product p53. After treatment with proteinase K, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) band of p53 yields a single, discrete 157-nucleotide RNA, which was cloned, sequenced, and identified as 5.8S rRNA. 5.8S rRNA was obtained only after proteolysis of the p53 SDS-PAGE band. Free 5.8S rRNA did not comigrate with p53 in SDS-PAGE. This RNA was only immunoprecipitated from cells containing p53. Protein-free RNA obtained by proteolysis of the p53 band hybridized to the single-stranded DNA vector containing the antisense sequence of 5.8S rRNA. The covalence of the p53-5.8S rRNA linkage was demonstrated by the following findings: (i) p53 and the linked 5.8S rRNA comigrated in SDS-PAGE; (ii) only after treatment of the p53-RNA complex with proteinase K did the 5.8S rRNA migrate differently from p53-linked 5.8S rRNA; and (iii) this isolated RNA was found linked to phosphoserine, presumably at the 5' end. Covalent linkage to the single, specific RNA suggests that p53 may be involved in regulating the expression or function of 5.8S rRNA.
Mol Cell Biol 1992 Nov
PMID:p53 is covalently linked to 5.8S rRNA. 140 86

Testicular steroidogenic enzymes in the microsomal fraction from immature pigs were investigated for the effects of phospholipids of known structure on androgen and 16-androstene biosynthesis. Untreated (control) microsomes metabolized pregnenolone to 17-hydroxypregnenolone, DHA and small quantities of progesterone, 17-hydroxyprogesterone, androstenedione and testosterone; and to 5,16-androstadien-3 beta-ol (andien-beta) and 4,16-androstadienone (dienone) in the 16-androstene pathway. Phosphatidyl(P)-serine, P-glycerol, P-ethanolamine, P-inositol, P-choline and phosphatidic acid did not significantly alter the 17-hydroxylase/C-17,20 lyase or "andien-beta-synthetase" activities. Thus, the C21 side-chain cleavage reactions appeared not to be dependent upon phospholipids for optimal activity. The conversion of pregnenolone to 4-ene steroids (progesterone, 17-hydroxyprogesterone, androstenedione and testosterone) was inhibited by dilinoleoyl-phosphatidyl-choline, but other phospholipids tested were without effect. On the other hand, the conversion of andien-beta to dienone was inhibited by P-serine, P-inositol and P-cholines with short saturated or long polyunsaturated acyl chains. Therefore, the presence of these phospholipids in pregnenolone incubations had different consequences for 3 beta-hydroxysteroid dehydrogenase-isomerase activities. It is concluded that substrate specific 3 beta-HSD-isomerases exist for androgen and 16-androstene biosynthesis and that phospholipids may play an intrinsic role in their catalytic activity.
J Steroid Biochem Mol Biol 1992 Apr
PMID:Identification of phospholipids capable of modulating the activities of some enzymes involved in androgen and 16-androstene biosynthesis in the immature pig testis. 156 81

Gap junctions are membrane channels that permit the interchange of ions and other low-molecular-weight molecules between adjacent cells. Rous sarcoma virus (RSV)-induced transformation is marked by an early and profound disruption of gap-junctional communication, suggesting that these membrane structures may serve as sites of pp60v-src action. We have begun an investigation of this possibility by identifying and characterizing putative proteins involved in junctional communication in fibroblasts, the major cell type currently used to study RSV-induced transformation. We found that uninfected mammalian fibroblasts do not appear to contain RNA or protein related to connexin32, the major rat liver gap junction protein. In contrast, vole and mouse fibroblasts contained a homologous 3.0-kilobase RNA similar in size to the heart tissue RNA encoding the gap junction protein, connexin43. Anti-connexin43 peptide antisera specifically reacted with three proteins of approximately 43, 45 and 47 kilodaltons (kDa) from communicating fibroblasts. Gap junctions of heart cells contained predominantly 45- and 47-kDa species similar to those found in fibroblasts. Uninfected fibroblast 45- and 47-kDa proteins were phosphorylated on serine residues. Phosphatase digestions of 45- and 47-kDa proteins and pulse-chase labeling studies indicated that these proteins represented phosphorylated forms of the 43-kDa protein. Phosphorylation of connexin protein appeared to occur shortly after synthesis, followed by an equally rapid dephosphorylation. In comparison with these results, connexin43 protein in RSV-transformed fibroblasts contained both phosphotyrosine and phosphoserine. Thus, the presence of phosphotyrosine in connexin43 correlates with the loss of gap-junctional communication observed in RSV-transformed fibroblasts.
Mol Cell Biol 1990 Apr
PMID:Phosphorylation of connexin43 gap junction protein in uninfected and Rous sarcoma virus-transformed mammalian fibroblasts. 169 Aug 50

The product of the HER-2 proto-oncogene, p185HER-2, was found to be amplified approximately 10-fold in the human breast carcinoma cell line, BT474, compared to a cell line, HBL-100, derived from normal breast tissue. To explore the possible role of p185HER-2 in growth of the breast carcinoma cells, we investigated factors that may modulate cell growth and phosphorylation of the HER-2 protein product. Two growth factors, epidermal growth factor (EGF) and insulin, stimulated phosphorylation of the HER-2 protein product. In response to insulin, the phosphoserine and phosphothreonine content in p185HER-2 was transiently enhanced about 6-fold. When EGF was added to BT474 cells there was 2- to 3-fold enhanced phosphorylation of serine and threonine residues in p185HER-2 which was maintained for at least 60 min. Although p185HER-2 has been found to be phosphorylated on tyrosine residues following EGF treatment of several different cell types, we estimate that less than 1% of the protein contained phosphotyrosine in the BT474 cells.
Mol Cell Endocrinol 1990 Mar 05
PMID:Insulin and epidermal growth factor stimulate phosphorylation of p185HER-2 in the breast carcinoma cell line, BT474. 169 19

Extracts of bakers' yeast (Saccharomyces cerevisiae) contain protein-tyrosine kinase activity that can be detected with a synthetic Glu-Tyr copolymer as substrate (G. Schieven, J. Thorner, and G.S. Martin, Science 231:390-393, 1986). By using this assay in conjunction with ion-exchange and affinity chromatography, a soluble tyrosine kinase activity was purified over 8,000-fold from yeast extracts. The purified activity did not utilize typical substrates for mammalian protein-tyrosine kinases (enolase, casein, and histones). The level of tyrosine kinase activity at all steps of each preparation correlated with the content of a 40-kDa protein (p40). Upon incubation of the most highly purified fractions with Mn-ATP or Mg-ATP, p40 was the only protein phosphorylated on tyrosine. Immunoblotting of purified p40 or total yeast extracts with antiphosphotyrosine antibodies and phosphoamino acid analysis of 32P-labeled yeast proteins fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the 40-kDa protein is normally phosphorylated at tyrosine in vivo. 32P-labeled p40 immunoprecipitated from extracts of metabolically labeled cells by affinity-purified anti-p40 antibodies contained both phosphoserine and phosphotyrosine. The gene encoding p40 (YPK1) was cloned from a yeast genomic library by using oligonucleotide probes designed on the basis of the sequence of purified peptides. As deduced from the nucleotide sequence of YPK1, p40 is homologous to known protein kinases, with features that resemble known protein-serine kinases more than known protein-tyrosine kinases. Thus, p40 is a protein kinase which is phosphorylated in vivo and in vitro at both tyrosine and serine residues; it may be a novel type of autophosphorylating tyrosine kinase, a bifunctional (serine/tyrosine-specific) protein kinase, or a serine kinase that is a substrate for an associated tyrosine kinase.
Mol Cell Biol 1990 Dec
PMID:Novel yeast protein kinase (YPK1 gene product) is a 40-kilodalton phosphotyrosyl protein associated with protein-tyrosine kinase activity. 170 Oct 15


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