Abstract
Vesicles of sarcoplasmic reticulum from rabbit muscle can be loaded with cholesterol to at least 20 mol% with respect to endogenous sarcoplasmic-reticulum phospholipid without effect on the ATPase activity at 32 degrees C. This applies both to sarcoplasmic-reticulum vesicles in which the ATPase activity is stably coupled to Ca2+ accumulation, and to sarcoplasmic-reticulum vesicles in which the sarcoplasmic-reticulum ATPase is activated severalfold by fully uncoupling the enzyme from net Ca2+ accumulation. Since the incorporation of cholesterol causes a large decrease in fluidity of sarcoplasmic-reticulum phospholipid bilayer, these results for sarcoplasmic reticulum raise the more general question of whether bilayer fluidity is important in modulating the function of membrane proteins under physiological conditions as is widely assumed, or whether the function of membrane proteins may be effectively buffered under normal operating conditions against changes in bilayer fluidity due to extraneous agents.
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Selected References
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- Hubbell W. L., McConnell H. M. Spin-label studies of the excitable membranes of nerve and muscle. Proc Natl Acad Sci U S A. 1968 Sep;61(1):12–16. doi: 10.1073/pnas.61.1.12. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MARTONOSI A., FERETOS R. SARCOPLASMIC RETICULUM. II. CORRELATION BETWEEN ADENOSINE TRIPHOSPHATASE ACTIVITY AND CA++ UPTAKE. J Biol Chem. 1964 Feb;239:659–668. [PubMed] [Google Scholar]
- Madden T. D., Chapman D., Quinn P. J. Cholesterol modulates activity of calcium-dependent ATPase of the sarcoplasmic reticulum. Nature. 1979 Jun 7;279(5713):538–541. doi: 10.1038/279538a0. [DOI] [PubMed] [Google Scholar]
- Richards C. D., Martin K., Gregory S., Keightley C. A., Hesketh T. R., Smith G. A., Warren G. B., Metcalfe J. C. Degenerate perturbations of protein structure as the mechanism of anaesthetic action. Nature. 1978 Dec 21;276(5690):775–779. doi: 10.1038/276775a0. [DOI] [PubMed] [Google Scholar]
- Scarpa A., Baldassare J., Inesi G. The effect of calcium ionophores on fragmented sarcoplasmic reticulum. J Gen Physiol. 1972 Dec;60(6):735–749. doi: 10.1085/jgp.60.6.735. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Warren G. B., Houslay M. D., Metcalfe J. C., Birdsall N. J. Cholesterol is excluded from the phospholipid annulus surrounding an active calcium transport protein. Nature. 1975 Jun 26;255(5511):684–687. doi: 10.1038/255684a0. [DOI] [PubMed] [Google Scholar]
- Warren G. B., Toon P. A., Birdsall N. J., Lee A. G., Metcalfe J. C. Reconstitution of a calcium pump using defined membrane components. Proc Natl Acad Sci U S A. 1974 Mar;71(3):622–626. doi: 10.1073/pnas.71.3.622. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Warren G. B., Toon P. A., Birdsall N. J., Lee A. G., Metcalfe J. C. Reversible lipid titrations of the activity of pure adenosine triphosphatase-lipid complexes. Biochemistry. 1974 Dec 31;13(27):5501–5507. doi: 10.1021/bi00724a008. [DOI] [PubMed] [Google Scholar]