title: Phosphorylation of multiple sites in a 15,000 dalton proteolipid from rat skeletal muscle sarcolemma, catalyzed by adenosine 3',5'-monophosphate-dependent and calcium/phospholipid-dependent protein kinases.
abstract: This study reports a partial characterization of a 15,000 dalton (15 kDa) proteolipid present in rat skeletal muscle sarcolemma. The proteolipid is phosphorylated by both cyclic AMP-dependent and calcium/phospholipid-dependent protein kinases, displays an isoelectric point (pI) of 5.9, and can be extracted from sarcolemma by acidified chloroform/methanol (2:1) or non-ionic detergents. Phosphoamino acid analysis and tryptic fingerprinting of the phosphorylated proteolipid indicate that both cyclic AMP- and calcium/phospholipid-dependent protein kinases predominantly phosphorylate serine residue(s) on a single tryptic peptide. Additivity experiments and thermolytic fingerprinting demonstrate a minimum of two distinct phosphorylation sites on the proteolipid, the phosphorylation of which is independently catalyzed by cyclic AMP-dependent and calcium/phospholipid-dependent protein kinases in vitro. This sarcolemma proteolipid, which appears to be identified to a sarcolemma protein previously reported to be phosphorylated upon addition of insulin in a GTP-dependent manner (Walaas, O., Walaas, E., Rye-Alertsen, A. and Horn, R.S. (1979) Mol. Cell. Endocrinol. 16, 45-55), therefore represents a possible membrane target for those neuronal and hormonal stimuli which can regulate cyclic AMP-dependent or calcium/phospholipid-dependent protein kinase activities in skeletal muscle.
authors.affiliation: Institute of Medical Biochemistry, University of Oslo (Norway).
authors.forename: S I
authors.initials: SI
authors.lastname: Walaas
authors.forename: R S
authors.initials: RS
authors.lastname: Horn
authors.forename: K A
authors.initials: KA
authors.lastname: Albert
authors.forename: A
authors.initials: A
authors.lastname: Adler
authors.forename: O
authors.initials: O
authors.lastname: Walaas
mesh_terms: D000818:Animals; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism*; D010743:Phospholipids / Q000032:analysis / Q000302:isolation & purification; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism*; D051381:Rats; D012508:Sarcolemma / Q000378:metabolism*
chemical_list: D010743:Phospholipids; D011510:Proteolipids; D011494:Protein Kinases; D011493:Protein Kinase C