Adjunctive use of inhaled nitric oxide during implantation of a left ventricular assist device

Human erythrocyte protein phosphatase 2A, which comprises a 34-kDa catalytic C subunit, a 63-kDa regulatory A subunit and a 74-kDa regulatory B' (delta) subunit, was phosphorylated at serine residues of B' in vitro by cAMP-dependent protein kinase (A-kinase). In the presence and absence of 0.5 microM okadaic acid (OA), A-kinase gave maximal incorporation of 1.7 and 1.0 mol of phosphate per mol of B', respectively. The Km value of A-kinase for CAB' was 0.17 +/- 0.01 microM in the presence of OA. The major in vitro phosphorylation sites of B' were identified as Ser-60, -75 and -573 in the presence of OA, and Ser-75 and -573 in the absence of OA. Phosphorylation of B' did not dissociate B' from CA, and stimulated the molecular activity of CAB' toward phosphorylated H1 and H2B histones, 3.8- and 1.4-fold, respectively, but not toward phosphorylase a.