Effect of lipid composition on the calcium/adenosine 5'-triphosphate coupling ratio of the Ca2+-ATPase of sarcoplasmic reticulum.
The Ca2+-ATPase of sarcoplasmic reticulum was purified and depleted of proteolipids by solubilization in Triton X-100 and by fractionation on a DE-52 column. The protein reconstituted by deoxycholate-cholate dialysis at low lipid to protein ratios (2-5 mg of lipid/mg of protein), with either dioleoylphosphatidylethanolamine or monogalactosyldiglyceride, exhibited high initial rates of ATP-dependent Ca2+ uptake [300-900 nmol min-1 (mg of protein)-1] and coupling ratios (Ca2+ transported/ATP hydrolyzed) up to 1.2. Ca2+-ATPase reconstituted with lipids of increasing degrees of methylation (dioleoylphosphatidylethanolamine, dioleoylmonomethylphosphatidylethanolamine, dioleoyldimethylphosphatidylethanolamine and dioleoylphosphatidylcholine) or increasing degrees of glycosylation (monogalactosyldiglyceride and digalactosyldiglyceride) revealed a progressive decrease in both ATP-dependent Ca2+-uptake and coupling ratios. The rate and extent of Ca2+ uptake decreased as the dioleoylphosphatidylethanolamine/dioleoylphosphatidylcholine or monogalactosyldiglyceride/dioleoylphosphatidylcholine molar ratios in the reconstituted vesicles were reduced. Vesicles reconstituted with high molar ratios of dioleoylphosphatidylethanolamine/dioleoylphosphatidylcholine or monogalactosyldiglyceride/dioleoylphosphatidylcholine and at a high lipid to protein ratio became leaky and released the Ca2+ accumulated inside the vesicles when the temperature of the incubation mixture was increased (e.g., from 20 to 37 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002784:Cholesterol / Q000494:pharmacology*; D005614:Freeze Fracturing; D007700:Kinetics; D008051:Lipid Bilayers; D008563:Membrane Lipids / Q000502:physiology*; D008854:Microscopy, Electron; D010743:Phospholipids / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000648:ultrastructure; D013329:Structure-Activity Relationship
D008051:Lipid Bilayers; D008563:Membrane Lipids; D010743:Phospholipids; D000255:Adenosine Triphosphate; D002784:Cholesterol; D000252:Calcium-Transporting ATPases; D002118:Calcium