Occurrence and characteristics of a rapid exchange of phosphate oxygens catalyzed by sarcoplasmic reticulum vesicles

Journal Article · Thu May 10 00:00:00 EDT 1973 · J. Biol. Chem.; (United States)

OSTI ID:7361429

Kanazawa, T; Boyer, P D

Sarcoplasmic reticulum vesicles prepared from rabbit skeletal muscle catalyze a rapid P/sub i/ reversible HOH exchange in the presence of Mg/sup 2 +/ and absence of ATP and Ca/sup 2 +/. The capacity for oxygen exchange is about 14 times the potential capacity for ATP cleavage in the presence of Ca/sup 2 +/. No detectable exchange is found without added MgCl/sub 2/. The exchange is unaffected by oligomycin, 2,4-dinitrophenol, or ouabain, but strongly inhibited by low concentrations of Ca/sup 2 +/ in the medium. The Ca/sup 2 +/ ion concentration giving a half-maximum inhibition is 2.0 ..mu..M in the presence of 5 mM MgCl/sub 2/. A Hill plot of the Ca/sup 2 +/ inhibition gives a straight line with a Hill coefficient of 1.8. The Ca/sup 2 +/ inhibition is competitively overcome by additional Mg/sup 2 +/. The P/sub i/ reversible HOH exchange is almost completely inhibited by the detergent Triton X-100 at low concentrations in which the ATPase activity is not disturbed. Sarcoplasmic reticulum vesicles are phosphorylated by P/sub i/ in the presence of Mg/sup 2 +/ and absence of Ca/sup 2 +/ under conditions similar to those for the P/sub i/ reversible HOH exchange. The phosphorylation requires Mg/sup 2 +/ and is strongly inhibited by low concentrations of Ca/sup 2 +/. The response of the phosphorylation to Ca/sup 2 +/ is quite similar to that of the P/sub i/ reversible HOH exchange; the Ca/sup 2 +/ ion concentration giving a half-maximum inhibition is 2.0 ..mu..M in the presence of 5 mM MgCl/sub 2/, and the Hill coefficient is about 2.0. The various properties of the exchange give strong support to the probability that it results from reversal of steps in the over-all process associated with Ca/sup 2 +/ transport driven by ATP cleavage.

• OSTI ID: 7361429
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 248:9; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
ANIMALS
ANTIBIOTICS
AROMATICS
ATP
ATP-ASE
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
CALCIUM
CARBOHYDRATES
CARDIOTONICS
CATALYSIS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CLEAVAGE
CRYOGENIC FLUIDS
CRYSTAL STRUCTURE
DINITROPHENOL
DRUGS
ELEMENTS
ENZYMES
ESTERASES
FLUIDS
GLYCOSIDES
HALIDES
HALOGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
KINETICS
MAGNESIUM CHLORIDES
MAGNESIUM COMPOUNDS
MAMMALS
METALS
MICROSTRUCTURE
MUSCLES
NITRO COMPOUNDS
NONMETALS
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OUABAIN
OXYGEN
OXYGEN COMPOUNDS
PHENOLS
PHOSPHATASES
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHOSPHORYLATION
RABBITS
REACTION KINETICS
STEROIDS
STROPHANTIN
VERTEBRATES