Effects of cholesterol on the interaction of Ca2(+)-ATPase with 1-palmitoyl-2-oleoylphosphatidylethanolamine. An FTIR study.
Ca2(+)-ATPase from rabbit skeletal muscle has been isolated, purified, and reconstituted into vesicles containing binary mixtures of 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE)/cholesterol. Fourier transform infrared spectroscopy (FTIR) was used to investigate the effect of protein on the thermotropic behavior of POPE in these reconstituted ternary complexes. The CH2 symmetric stretching modes of the phospholipid acyl chains near 2850 cm-1 served as an index of the melting process. The thermotropic transition of the POPE component in a 103:12:1 (POPE/cholesterol/Ca2(+)-ATPase) complex was shifted to lower temperatures compared with a protein-free binary lipid mixture of the same relative proportions. When combined with differential scanning calorimetric (DSC) data for the binary (POPE/cholesterol) lipid systems, this observation suggests that Ca2(+)-ATPase preferentially sequesters 15-35 molecules of POPE from the lipid mixture and therefore excludes cholesterol from its immediate environment. Higher levels of cholesterol in ternary complexes progressively eliminate the cooperative POPE melting event.
Yang
J
J
Department of Chemistry, Rutgers University, Newark College of Arts and Sciences, NJ 071012.
Anderle
G L
GL
Mendelsohn
R
R
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000502:physiology*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D011817:Rabbits; D013055:Spectrophotometry, Infrared
D010714:Phosphatidylethanolamines; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; D002784:Cholesterol; D000252:Calcium-Transporting ATPases