Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ARPP-21 (cAMP-regulated phosphoprotein, Mr = 21,000 as determined by SDS/PAGE) is a major cytosolic substrate for cAMP-stimulated protein phosphorylation in dopamine-innervated regions of rat CNS (Walaas et al., 1983c). This acidic phosphoprotein has now been identified in bovine caudate nucleus cytosol and purified to homogeneity from this source. The purification procedure involved diethylaminoethyl-cellulose chromatography, ammonium sulfate fractionation, phenyl-Sepharose CL-4B chromatography, and fast protein liquid chromatography using Mono Q anion-exchange resin. Two isoforms of ARPP-21 (ARPP-21A and ARPP-21B) were obtained, which were present in approximately equal amounts in the starting material. ARPP-21A was purified 2610-fold with a final yield of 20% and ARPP-21B was purified 2940-fold with a final yield of 21%. The purified preparations of both isoforms were judged to be homogenous by SDS/PAGE. ARPP-21A and ARPP-21B yielded identical 2-dimensional thin-layer tryptic phosphopeptide maps, identical amino acid compositions and closely related, but distinct, reverse-phase high-pressure liquid chromatograms of tryptic digests. The amino acid composition of ARPP-21 showed a high content of glutamic acid/glutamine, and no methionine, tryptophan, tyrosine, phenylalanine, or histidine. ARPP-21 was stable to heat denaturation and to 50% (vol/vol) ethanol treatment and was partially soluble at pH 2. The Mr determined for ARPP-21 by SDS/PAGE was 21,000. The Stokes radius of ARPP-21 was 26.3 A, and the sedimentation coefficient of ARPP-21 was 1.3 S; these values yield a calculated molecular mass of 13,700 Da and a frictional ratio of 1.7, indicative of an elongated tertiary structure. ARPP-21 was an excellent substrate for cAMP-dependent protein kinase and was either not phosphorylated or only poorly phosphorylated by cGMP-dependent protein kinase, calcium/calmodulin-dependent protein kinase I, calcium/calmodulin-dependent protein kinase II, casein kinase II, or protein kinase C. The purified catalytic subunit of cAMP-dependent protein kinase catalyzed the incorporation of 1.2 mol phosphate/mol purified ARPP-21. Phosphorylation occurred exclusively on seryl residues. Phospho-ARPP-21 was dephosphorylated effectively by protein phosphatase-1 or -2A, but not by protein phosphatase-2B or -2C. Rabbit polyclonal and mouse monoclonal antibodies were prepared to purified ARPP-21. These antibodies specifically immunoprecipitated ARPP-21, which was found to be highly enriched in the caudate nucleus and putamen of monkey brain.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:ARPP-21, a cyclic AMP-regulated phosphoprotein enriched in dopamine-innervated brain regions. I. Purification and characterization of the protein from bovine caudate nucleus. 253 84

ARPP-21 (cAMP-regulated phosphoprotein, Mr = 21,000 as determined by SDS-PAGE) is a major cytosolic substrate for cAMP-stimulated protein phosphorylation in dopamine-innervated regions of the rat CNS. It has recently been purified to homogeneity from bovine caudate nucleus and characterized (Hemmings and Greengard, 1989). ARPP-21 is isolated as 2 isoforms, ARPP-21A and ARPP-21B. The amino acid sequence of purified bovine ARPP-21B has now been determined by gas-phase sequencing. The S-14C-carboxymethylated protein was subjected to enzymatic cleavage with trypsin, chymotrypsin, subtilisin, and endoproteinase Lys-C. The resulting peptides were purified by high-performance liquid chromatography, and selected peptides were subjected to amino acid analysis and/or amino acid sequencing by automated Edman degradation. ARPP-21B consists of a single NH2-terminal blocked polypeptide chain of 88 residues, with a calculated molecular mass of 9561 Da, including an NH2-terminal acetyl group inferred by deblocking with an acylaminopeptidase. This molecular mass is significantly lower than earlier estimates based on SDS-PAGE or hydrodynamic measurements. The seryl residue phosphorylated by cAMP-dependent protein kinase (Hemmings et al., 1989) is located at position 55. The molecule contains 1 cysteinyl residue, at position 71, and contains no methionyl, tyrosyl, phenylalanyl, tryptophanyl, or histidinyl residues. Determination of the primary structure of ARPP-21, one of several phosphoproteins localized to dopaminoceptive neurons in the basal ganglia, provides a framework for further investigations into the molecular mechanisms involved in dopaminergic neurotransmission.
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PMID:ARPP-21, a cyclic AMP-regulated phosphoprotein enriched in dopamine-innervated brain regions. I. Amino acid sequence of ARPP-21B from bovine caudate nucleus. 255 36

This study describes a cyclic AMP-regulated phosphoprotein that displays a distinct cellular and regional distribution in rat brain. The protein is found only in neostriatal regions, where it is enriched in nerve cells and not in afferent or efferent axons or in glial cells. On subcellular fractionation, it appears tightly associated with particulate components, possibly the synaptic plasma membrane fraction. The protein may therefore be specifically enriched in dendrites and/or somata of neostriatal neurons. Following phosphorylation in vitro with [gamma-32P]ATP and cyclic AMP-dependent protein kinase, the protein contains phosphoseryl residues on multiple thermolytic peptides. The specific cellular and subcellular localization we have observed suggests that this protein, termed ARPP-39 (cyclic AMP-regulated phosphoprotein, M(r) = 39,000) may be important in receptor-regulated, cyclic AMP-mediated functions in distinct neostriatal neurons.
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PMID:ARPP-39, a membrane-associated substrate for cyclic AMP-dependent protein kinase present in neostriatal neurons. 821 21