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Reconstitution of Calmodulin‐Sensitive Adenylate Cyclase from Bovine Brain with Phosphatidylcholine Liposomes
Author(s) -
Yeager Robert E.,
Heideman Warren,
Olwin Bradley B.,
Keller Charles H.,
Schmidt John W.,
Shattuck Rebecca L.,
Storm Daniel R.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb12889.x
Subject(s) - liposome , phospholipid , phosphatidylcholine , chemistry , cyclase , enzyme , biochemistry , adenylate kinase , chromatography , membrane
A partially purified calmodulin (CaM)‐sensitive adenylate cyclase from bovine cerebral cortex was reconstituted with a series of phosphatidylcholine liposomes having variable fatty acid composition. The enzyme was successfully associated with dimyristoyl, dipalmitoyl, distearoyl, and dioleoylphosphatidylcholine liposomes. The specific activity of the enzyme in the various liposomes varied over a 4.6‐fold range indicating some degree of specificity for fatty acid composition. The adenylate cyclase‐liposome preparation retained sensitivity to both CaM and 5′‐guanylylimidodiphosphate (GppNHp). Arrhenius plots of enzyme activity in the four different liposome preparations all exhibited a pronounced discontinuity at 30°C ± 2, even though the bulk‐phase thermal transition points for the liposomes varied from −20 to 54°C. Fluorescence anisotropy studies of reconstituted liposome systems illustrated that incorporation of protein did not alter the normal‐phase transition point of these lipids. Since Arrhenius plots of the enzyme in Lubrol PX, prior to reconstitution with lipids, were strictly linear, it is concluded that the breaks at 30°C may be the effect of a local enzyme‐phospholipid environment. It appears that this adenylate cyclase is not particularly sensitive to phase transitions of the bulk lipid phase. The phospholipid reconstituted enzyme system appears suitable for examination of the influence of lipids on the CaM‐sensitive adenylate cyclase.