TY - JOUR T1 - DARPP-32, a dopamine- and adenosine 3':5'-monophosphate-regulated phosphoprotein enriched in dopamine-innervated brain regions. II. Purification and characterization of the phosphoprotein from bovine caudate nucleus JF - The Journal of Neuroscience JO - J. Neurosci. SP - 99 LP - 110 DO - 10.1523/JNEUROSCI.04-01-00099.1984 VL - 4 IS - 1 AU - HC Hemmings, Jr AU - AC Nairn AU - DW Aswad AU - P Greengard Y1 - 1984/01/01 UR - http://www.jneurosci.org/content/4/1/99.abstract N2 - DARPP-32 is a neuronal phosphoprotein of Mr = 32,000, originally identified in rat brain (Walaas, S.I., D.W. Aswad, and P. Greengard (1983) Nature 301: 69–72). This protein has now been identified in bovine caudate nucleus cytosol and purified 435-fold to apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purification procedure involved acid extraction at pH 2, CM-cellulose chromatography, DEAE-cellulose chromatography, hydroxylapatite chromatography, and gel filtration on Ultrogel AcA 44. The purified catalytic subunit of cAMP-dependent protein kinase catalyzed the incorporation of 0.96 mol of phosphate/mol of purified DARPP-32. Phosphorylation occurred exclusively on threonine. The isoelectric point of dephospho-DARPP-32 was 4.7, and that of phospho- DARPP-32 was 4.6. The amino acid composition showed a high content of glutamate/glutamine and proline, and a low content of hydrophobic amino acids. DARPP-32 was found to have a Stokes radius of 34 A and a sedimentation coefficient of 2.05 S, indicating that it exists as an elongated monomer. ER -