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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reversible protein phosphorylation plays important roles in signal transduction. One gene, prpA, encoding a protein similar to eukaryotic types of phosphoprotein phosphatases PP1, PP2A, and PP2B, was cloned from the nitrogen-fixing cyanobacterium Anabaena sp. strain PCC 7120. Interestingly, a eukaryotic-type protein kinase gene, pknE, was found 301 bp downstream of prpA. This unusual genetic arrangement provides the opportunity for study about how the balance between protein phosphorylation and dephosphorylation can regulate cellular activities. Both proteins were overproduced in Escherichia coli and used to raise polyclonal antibodies. Immunodetection and RNA/DNA hybridization experiments suggest that these two genes are unlikely to be coexpressed, despite their close genetic linkage. PrpA is expressed constitutively under different nitrogen conditions, while PknE expression varies according to the nature of the nitrogen source. Inactivation analysis in vivo suggests that PrpA and PknE function to ensure a correct level of phosphorylation of the targets in order to regulate similar biological processes such as heterocyst structure formation and nitrogen fixation.
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PMID:Molecular and genetic analysis of two closely linked genes that encode, respectively, a protein phosphatase 1/2A/2B homolog and a protein kinase homolog in the cyanobacterium Anabaena sp. strain PCC 7120. 957 44

The structural gene for a putative PPP family protein-serine/threonine phosphatase from the microcystin-producing cyanobacterium Microcystis aeruginosa PCC 7820, pp1-cyano1, was cloned. The sequence of the predicted gene product, PP1-cyano1, was 98% identical to that of the predicted product of an open reading frame, pp1-cyano2, from a cyanobacterium that does not produce microcystins, M. aeruginosa UTEX 2063. By contrast, PP1-cyano1 displayed less than 20% identity with other PPP family protein phosphatases from eukaryotic, archaeal, or other bacterial organisms. PP1-cyano1 and PP1-cyano2 were expressed in Escherichia coli and purified to homogeneity. Both enzymes exhibited divalent metal dependent phosphohydrolase activity in vitro toward phosphoserine- and phosphotyrosine-containing proteins and 3-phosphohistidine- and phospholysine-containing amino acid homopolymers. This multifunctional potential also was apparent in samples of PP1-cyano1 and PP1-cyano2 isolated from M. aeruginosa. Catalytic activity was insensitive to okadaic acid or the cyanobacterially produced cyclic heptapeptide, microcystin-LR, both potent inhibitors of mammalian PP1 and PP2A. PP1-cyano1 and PP1-cyano2 displayed diadenosine tetraphosphatase activity in vitro. Diadenosine tetraphosphatases share conserved sequence features with PPP family protein phosphatases. The diadenosine tetraphosphatase activity of PP1-cyano1 and PP1-cyano2 confirms that these enzymes share a common catalytic mechanism.
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PMID:Cyanobacterial PPP family protein phosphatases possess multifunctional capabilities and are resistant to microcystin-LR. 1018 82