Transmembrane Ca2+ gradient-mediated phosphatidylcholine modulating sarcoplasmic reticulum Ca2+-ATPase

Yaping Tu, Hong Xu, Fuyu Yang

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Abstract

The sarcoplasmic reticulum (SR) Ca2+-ATPase was purified and reconstituted into the sealed phospholipids vesicles with or without transmembrane Ca2+ gradient. The role ofphospholipids, especially phosphatidylcholine(PC), in the modulation of Ca2+-ATPase by transmembrane Ca2+ gradient was investigated. The results are as follows. (i) Incubated with phospholipids, the enzyme activity of the delipidated Ca2+-ATPase is inhibited by Ca2+ and the highest inhibition is observed in the presence of PC. (ii) When there exists a transmembrane Ca2+ gradient (higher Ca2+ concentration inside vesicles, 1 000 μmol/L:50 μmol/L, similar to the physiological condition), the inhibition of Ca2+-ATPase by transmembrane Ca2+ gradient can be only observed in the vesicles containing PC:PE, but not in those containing PS:PE or PG:PE. The highest inhibition is obtained at a 50:50 molar ratio of PC:PE. (iii) By comparing the effects of PC differing in acyl chains, higher inhibition of Ca2+-ATPase is observed in vesicles containing DPPC:PE and DOPC:PE, while no inhibition in DMPC:PE vesicles. (iv) If the transmembrane Ca2+ gradient is in the inverse direction, the enzyme activity of Ca2+-ATPase is inhibited whenever reconstituted with acidic or neutral phospholipids.

Original languageEnglish
Pages (from-to)713-721
Number of pages9
JournalScience in China. Series B, Chemistry, life sciences & earth sciences
Volume38
Issue number6
StatePublished - Jun 1995
Externally publishedYes

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vesicle
phospholipid
Phospholipids
Enzyme activity
enzyme activity
Adenosine Triphosphatases
Modulation

Cite this

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title = "Transmembrane Ca2+ gradient-mediated phosphatidylcholine modulating sarcoplasmic reticulum Ca2+-ATPase",
abstract = "The sarcoplasmic reticulum (SR) Ca2+-ATPase was purified and reconstituted into the sealed phospholipids vesicles with or without transmembrane Ca2+ gradient. The role ofphospholipids, especially phosphatidylcholine(PC), in the modulation of Ca2+-ATPase by transmembrane Ca2+ gradient was investigated. The results are as follows. (i) Incubated with phospholipids, the enzyme activity of the delipidated Ca2+-ATPase is inhibited by Ca2+ and the highest inhibition is observed in the presence of PC. (ii) When there exists a transmembrane Ca2+ gradient (higher Ca2+ concentration inside vesicles, 1 000 μmol/L:50 μmol/L, similar to the physiological condition), the inhibition of Ca2+-ATPase by transmembrane Ca2+ gradient can be only observed in the vesicles containing PC:PE, but not in those containing PS:PE or PG:PE. The highest inhibition is obtained at a 50:50 molar ratio of PC:PE. (iii) By comparing the effects of PC differing in acyl chains, higher inhibition of Ca2+-ATPase is observed in vesicles containing DPPC:PE and DOPC:PE, while no inhibition in DMPC:PE vesicles. (iv) If the transmembrane Ca2+ gradient is in the inverse direction, the enzyme activity of Ca2+-ATPase is inhibited whenever reconstituted with acidic or neutral phospholipids.",
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AU - Xu, Hong

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AB - The sarcoplasmic reticulum (SR) Ca2+-ATPase was purified and reconstituted into the sealed phospholipids vesicles with or without transmembrane Ca2+ gradient. The role ofphospholipids, especially phosphatidylcholine(PC), in the modulation of Ca2+-ATPase by transmembrane Ca2+ gradient was investigated. The results are as follows. (i) Incubated with phospholipids, the enzyme activity of the delipidated Ca2+-ATPase is inhibited by Ca2+ and the highest inhibition is observed in the presence of PC. (ii) When there exists a transmembrane Ca2+ gradient (higher Ca2+ concentration inside vesicles, 1 000 μmol/L:50 μmol/L, similar to the physiological condition), the inhibition of Ca2+-ATPase by transmembrane Ca2+ gradient can be only observed in the vesicles containing PC:PE, but not in those containing PS:PE or PG:PE. The highest inhibition is obtained at a 50:50 molar ratio of PC:PE. (iii) By comparing the effects of PC differing in acyl chains, higher inhibition of Ca2+-ATPase is observed in vesicles containing DPPC:PE and DOPC:PE, while no inhibition in DMPC:PE vesicles. (iv) If the transmembrane Ca2+ gradient is in the inverse direction, the enzyme activity of Ca2+-ATPase is inhibited whenever reconstituted with acidic or neutral phospholipids.

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