IDENTIFICATION OF A NEW PHOSPHORYLATION SITE IN CARDIAC-MUSCLE PHOSPHOFRUCTOKINASE

The novel phosphorylation site (Ser(376)) that we discovered during in vitro studies of the troponin C- or calmodulin-induced phosphorylatio n of rabbit muscle phosphofructokinase [Zhao, Z., Malencik, D. A., and Anderson, S. R. (1991) Biochemistry 30, 2204] also undergoes phosphor ylation in the epinephrine-stimulated rabbit heart. Reversed-phase HPL C and/or iron chelate affinity chromatography performed on CNBr digest s of phosphofructokinase that had been isolated from epinephrine-treat ed hearts yields a largely phosphorylated peptide corresponding to ami no acid residues 371-378 of the enzyme. Mass spectrometry, gas phase s equencing, and amino acid analyses establish the structure and phospho rylation state of the peptide. (C) 1997 Academic Press.