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Purification and characterisation of p99, a nuclear modulator of protein phosphatase 1 activity
Author(s) -
Kreivi Jan-Peter,
Trinkle-Mulcahy Laura,
Lyon Carol E,
Morrice Nick A,
Cohen Philip,
Lamond Angus I
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)01485-3
Subject(s) - phosphatase , protein subunit , nucleolus , biochemistry , recombinant dna , microbiology and biotechnology , chemistry , biology , enzyme , gene , cytoplasm
We have purified a form of protein phosphatase 1 (PP1) from HeLa cell nuclei, in which the phosphatase is complexed to a regulatory subunit termed p99. We report here the cloning and characterisation of the p99 component. p99 mRNA is widely expressed in human tissues and immunofluorescence analysis with anti‐p99 antibodies showed a punctate nucleoplasmic staining with additional accumulations within the nucleolus. The C‐terminus of p99 contains seven RGG RNA‐binding motifs, followed by eleven decapeptide repeats containing six or more of the following conserved residues (GHRPHEGPGG), and finally a putative zinc finger domain. Recombinant p99 suppresses the phosphorylase phosphatase activity of PP1 by >90% and the canonical PP1‐binding motif on p99 (residues 396–401) is unusual in that the phenylalanine residue is replaced by tryptophan.