A proper transmembrane Ca2+ gradient is essential for the higher enzymatic activity of adenylate cyclase.
Adenylate cyclase from bovine brain cortex was reconstituted into liposomes with (1000 fold) or without transmembrane Ca2+ gradient. The highest enzyme activity (the active center of enzyme exposing outside) was observed in the vesicles with lower Ca2+ concentration outside (approximately 10(-6) M, similar to physiological condition). If the transmembrane Ca2+ gradient was in the inverse direction (i.e. higher Ca2+ concentration outside, 1 mM), a lowest enzyme activity would appear. Such a difference could be diminished following addition of A23187. Obtained results showed that a proper transmembrane Ca2+ gradient is essential for the optimal fluidity of phospholipid bilayer, favouring the formation of suitable conformation of adenylate cyclase with higher enzyme activity.
Yang
F Y
FY
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, China.
Tu
Y P
YP
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002417:Cattle; D002540:Cerebral Cortex / Q000201:enzymology; D002942:Circular Dichroism; D066298:In Vitro Techniques; D008564:Membrane Potentials; D011510:Proteolipids; D013050:Spectrometry, Fluorescence
D011510:Proteolipids; C020485:proteoliposomes; D000001:Calcimycin; D000262:Adenylyl Cyclases; D002118:Calcium