Pressure effects on sarcoplasmic reticulum: a Fourier transform infrared spectroscopic study.
The Ca2(+)-ATPase of sarcoplasmic reticulum is irreversibly inactivated by exposure to 1.5-2.0 kbar pressure for 30-60 min in a Ca2(+)-free medium; mono- or decavanadate (5 mM) or to a lesser extent Ca2+ (2-20 mM) protect against inactivation (Varga et al. (1986) J. Biol. Chem. 261, 13943-13956). The structural basis of these effects was analyzed by FTIR spectroscopy of sarcoplasmic reticulum in 2H2O medium. The inactivation of the Ca2(+)-ATPase at 1.5-2.0 kbar pressure in a Ca2(+)-free medium was accompanied by changes in the Amide II region of the spectrum (1550 cm-1), that are consistent with increased hydrogen-deuterium (H-2H) exchange, and by the enhancement of a band at 1630 cm-1 in the Amide I region, that is attributed to an increase in beta sheet. The frequency of the peak of the Amide I band shifted from about 1648 cm-1 at atmospheric pressure to 1642 cm-1 at approximately equal to 12.5 kbar pressure, suggesting a decrease in alpha helix, and an increase in beta and/or random coil structures. Upon releasing the pressure, the shift of the Amide I band was partially reversed. Vanadate (5 mM), and to a lesser extent Ca2+ (2-20 mM), protected the Ca2(+)-ATPase against pressure-induced changes both in the Amide I and Amide II regions of the spectrum, together with protection of ATPase activity. These observations establish a correlation between the conformation of the Ca2(+)-ATPase and its sensitivity to pressure. The involvement of the ATP binding domain of the Ca2(+)-ATPase in the pressure-induced structural changes is suggested by the decreased polarization of fluorescence of fluorescein 5'-isothiocyanate covalently attached to the enzyme.
Buchet
R
R
Department of Biochemistry and Molecular Biology, State University of New York, Syracuse 13210.
Carrier
D
D
Wong
P T
PT
Jona
I
I
Martonosi
A
A
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002942:Circular Dichroism; D004789:Enzyme Activation / Q000187:drug effects; D005454:Fluorescence Polarization; D006859:Hydrogen / Q000378:metabolism; D007700:Kinetics; D011312:Pressure; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism; D013055:Spectrophotometry, Infrared / Q000379:methods; D013329:Structure-Activity Relationship; D014638:Vanadates / Q000494:pharmacology
D014638:Vanadates; D006859:Hydrogen; D000252:Calcium-Transporting ATPases; D002118:Calcium