Biomaterial Database

Dependence of cardiac sarcoplasmic reticulum calcium pump activity on the phosphorylation status of phospholamban. 1991

J Colyer, and J H Wang

Department of Medical Biochemistry, University of Calgary, Alberta, Canada.

The application of electrophoretic resolution of the different phosphorylation species of pentameric phospholamban as a measure of phosphorylation stoichiometry was examined and verified. This enabled a critical evaluation of a number of issues central to current models of calcium pump regulation in cardiac sarcoplasmic reticulum. The phospholamban content of numerous preparations was calculated from 32P incorporation at a given stoichiometry, and compared with the respective calcium pump concentration (derived by comparison with a Coomassie-stained calibration curve of the fast-twitch skeletal muscle isozyme). A relationship of 2 mol of phospholamban:1 mol of ATPase resulted (phospholamban monomer:ATPase monomer), which was maintained throughout all vesicle subpopulations. The precise mechanism of coupling of phospholamban phosphorylation to calcium pump stimulation was probed, with particular emphasis on the individual contributions of each phosphorylated species (P1 to P5). This relationship could be adequately explained in three ways: (i) each phosphorylation event contributed equally to calcium pump stimulation; (ii) P1 and P2 were incapable of stimulating calcium pump activity, but full stimulation occurred upon generation of species P3; or (iii) the phosphospecies P1 was without effect on basal calcium pump activity, but successive phosphorylations contributed equally to stimulation. Finally, the functional implication of dual site phosphorylation of phospholamban (cAMP- and the endogenous calmodulin-dependent kinases) was examined. No change in calcium pump activity accompanied the second tier of phosphorylation over that achieved by the first.

UI	MeSH Term	Description	Entries
D009206	Myocardium	The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.	Muscle, Cardiac,Muscle, Heart,Cardiac Muscle,Myocardia,Cardiac Muscles,Heart Muscle,Heart Muscles,Muscles, Cardiac,Muscles, Heart
D010766	Phosphorylation	The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.	Phosphorylations
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002135	Calcium-Binding Proteins	Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS.	Calcium Binding Protein,Calcium-Binding Protein,Calcium Binding Proteins,Binding Protein, Calcium,Binding Proteins, Calcium,Protein, Calcium Binding,Protein, Calcium-Binding
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D000252	Calcium-Transporting ATPases	Cation-transporting proteins that utilize the energy of ATP hydrolysis for the transport of CALCIUM. They differ from CALCIUM CHANNELS which allow calcium to pass through a membrane without the use of energy.	ATPase, Calcium,Adenosinetriphosphatase, Calcium,Ca(2+)-Transporting ATPase,Calcium ATPase,Calcium Adenosinetriphosphatase,Adenosine Triphosphatase, Calcium,Ca2+ ATPase,Calcium-ATPase,ATPase, Ca2+,ATPases, Calcium-Transporting,Calcium Adenosine Triphosphatase,Calcium Transporting ATPases,Triphosphatase, Calcium Adenosine
D001693	Biological Transport, Active	The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.	Active Transport,Uphill Transport,Active Biological Transport,Biologic Transport, Active,Transport, Active Biological,Active Biologic Transport,Transport, Active,Transport, Active Biologic,Transport, Uphill
D012519	Sarcoplasmic Reticulum	A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.	Reticulum, Sarcoplasmic,Reticulums, Sarcoplasmic,Sarcoplasmic Reticulums
D017301	Ca(2+) Mg(2+)-ATPase	An enzyme that catalyzes the hydrolysis of ATP and is activated by millimolar concentrations of either Ca(2+) or Mg(2+). Unlike CA(2+)-TRANSPORTING ATPASE it does not require the second divalent cation for its activity, and is not sensitive to orthovanadate. (Prog Biophys Mol Biol 1988;52(1):1). A subgroup of EC 3.6.1.3.	ATPase, Calcium Magnesium,ATPase, Magnesium,Adenosinetriphosphatase, Calcium, Magnesium,Adenosinetriphosphatase, Magnesium,Calcium Magnesium ATPase,Calcium Magnesium Adenosinetriphosphatase,Magnesium ATPase,Magnesium Adenosinetriphosphatase,Adenosine Triphosphatase, Calcium, Magnesium,Adenosine Triphosphatase, Magnesium,Ca Mg-ATPase,Ca2+-Mg2+ ATPase,Calcium Magnesium Adenosine Triphosphatase,Mg2+-ATPase,Mg2+-Dependent ATPase,ATPase, Ca2+-Mg2+,ATPase, Mg2+-Dependent,Adenosinetriphosphatase, Calcium Magnesium,Ca Mg ATPase,Ca2+ Mg2+ ATPase,Magnesium Adenosine Triphosphatase,Mg2+ ATPase,Mg2+ Dependent ATPase