The effect of dicyclohexylcarbodiimide and cyclopiazonic acid on the difference FTIR spectra of sarcoplasmic reticulum induced by photolysis of caged-ATP and caged-Ca2+.
The photochemical release of Ca2+ from caged-Ca2+ in the absence of ATP, and the release of ATP from caged-ATP in the presence of Ca2+ induce characteristic difference FTIR spectra on rabbit sarcoplasmic reticulum that are related to the formation of Ca2-E1 and E approximately P intermediates of the Ca(2+)-ATPase, respectively. Dicyclohexylcarbodiimide (10 nmol/mg protein) abolished both the Ca(2+)-and ATP-induced difference FTIR spectra parallel with inhibition of ATPase activity. Cyclopiazonic acid (50 nmol/mg protein) inhibited the Ca(2+)-induced difference spectrum measured in the absence of ATP, but had no significant effect on the ATP-induced difference spectrum measured in the presence of 1 mM Ca2+. The dog kidney Na+,K(+)-ATPase did not give significant difference spectrum after photolysis of caged-ATP in Ca(2+)-free media containing 90 mM Na+ and 10 mM K+, with or without ouabain. We propose that both the Ca2+ and the ATP-induced difference FTIR spectra of the Ca(2+)-ATPase reflect the occupancy of the high-affinity Ca2+ transport site of the enzyme.
Buchet
R
R
Department of Biochemistry and Molecular Biology, State University of New York, Syracuse 13210.
Jona
I
I
Martonosi
A
A
D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry*; D000818:Animals; D002118:Calcium / Q000737:chemistry*; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology*; D005583:Fourier Analysis; D007211:Indoles / Q000494:pharmacology*; D010782:Photolysis; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry* / Q000187:drug effects
D007211:Indoles; D004024:Dicyclohexylcarbodiimide; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D002118:Calcium; C000543:cyclopiazonic acid