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Sarcolipin uncouples hydrolysis of ATP from accumulation of Ca2+ by the Ca2+-ATPase of skeletal-muscle sarcoplasmic reticulum

Record type: Article

Sarcolipin (SLN) is a small peptide found in the sarcoplasmic reticulum of skeletal muscle. It is predicted to contain a single hydrophobic transmembrane a-helix. Fluorescence emission spectra for the single Trp residue of SLN suggest that SLN incorporates fully into bilayers of dioleoylphosphatidylcholine, but only partially into bilayers of phosphatidylcholines with long (C22 or C24) fatty acyl chains. The fluorescence of SLN is quenched in bilayers of dibromostearoylphosphatidylcholine, also consistent with incorporation into the lipid bilayer. SLN was reconstituted with the Ca2+-ATPase of skeletal-muscle sarcoplasmic reticulum. Even at a 50:1 molar ratio of SLN/ATPase, SLN had no significant effect on the rate of ATP hydrolysis by the ATPase or on the Ca2+-dependence of ATP hydrolysis. However, at a molar ratio of SLN/ATPase of 2:1 or higher the presence of SLN resulted in a marked decrease in the level of accumulation of Ca2+ by reconstituted vesicles. The effect of SLN was structurally specific and did not result from a breakdown in the vesicular structure or from the formation of non-specific ion channels. Vesicles were impermeable to Ca2+ in the absence of ATP in the external medium. The effects of SLN on accumulation of Ca2+ can be simulated assuming that SLN increases the rate of slippage on the ATPase and the rate of passive leak of Ca2+ mediated by the ATPase. It is suggested that the presence of SLN could be important in non-shivering thermogenesis, a process in which heat is generated by hydrolysis of ATP by skeletal-muscle sarcoplasmic reticulum.

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Citation

Smith, W.S., Broadbridge, R., East, J.M. and Lee, A.G. (2002) Sarcolipin uncouples hydrolysis of ATP from accumulation of Ca2+ by the Ca2+-ATPase of skeletal-muscle sarcoplasmic reticulum Biochemical Journal, 361, (2), pp. 277-286.

More information

Submitted date: 30 July 2001
Published date: 1 January 2002
Keywords: calcium pump, coupling, reconstitution, thermogenesis

Identifiers

Local EPrints ID: 56392
URI: http://eprints.soton.ac.uk/id/eprint/56392
ISSN: 1470-8728
PURE UUID: 9e65729f-6e9d-4f69-be93-3b972d84c0bd

Catalogue record

Date deposited: 06 Aug 2008
Last modified: 17 Jul 2017 14:30

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Contributors

Author: W.S. Smith
Author: R. Broadbridge
Author: J.M. East
Author: A.G. Lee

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