Kinetic evidence for two nucleotide binding sites on the CaATPase of sarcoplasmic reticulum
- Univ. of the Pacific, San Francisco, CA (USA)
The CaATPase of sarcoplasmic reticulum was reacted with ({gamma}-{sup 32}P)ATP to form the covalent phosphoenzyme intermediate. Noncompetitive inhibition by reactive red-120 and chelation of calcium allowed the authors to monitor single-turnover kinetics of the phosphoenzyme reacting with water or added ADP at 0C. When ADP was added and the amount of product, ({gamma}-{sup 32}P)ATP, formed was measured, they found that added cold ATP did not interfere with the phosphoenzyme reacting with ADP. The authors conclude that ATP cannot bind where ADP binds, the phosphorylated active site. This implies that when ATP at high concentrations causes an acceleration of phosphoenzyme hydrolysis, it must do so by binding to an allosteric site. Considering the monoexponential nature of product formation they observed, simple one-nucleotide-site models cannot account for the above result.
- OSTI ID:
- 5596297
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:6; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ALKALINE EARTH METAL COMPOUNDS
ATP
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CALCIUM COMPOUNDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
ENDOPLASMIC RETICULUM
ENZYMES
HYDROLASES
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORYLATION
RADIOISOTOPES
REACTION KINETICS
SARCOPLASMIC RETICULUM