Burt J M, Langer G A
Biochim Biophys Acta. 1983 Mar 23;729(1):44-52. doi: 10.1016/0005-2736(83)90454-6.
Amphiphilic, cationic Polymyxin B is shown to displace Ca2+ from 'gas dissected' cardiac sarcolemma in a dose-dependent, saturable fashion. The Ca2+ displacement is only partially reversible, 57% and 63%, in the presence of 1 mM or 10 mM Ca2+, respectively. Total Ca2+ displaced by a non-specific cationic probe, lanthanum (La3+), at maximal displacing concentration (1 mM) was 0.172 +/- 0.02 nmol/microgram membrane protein. At 0.1 mM, Polymyxin B displaced 42% of the total La3+-displaceable Ca2+ or 0.072 +/- 0.01 nmol/microgram protein. 5 mM Polymyxin displaced Ca2+ in amounts equal to those displaced by 1 mM La3+. Pretreatment of the membranes with neuraminidase (removal of sialic acid) and protease leads to a decrease in La3+-displaceable Ca2+ but to an increase in the fraction displaced by 0.1 mM Polymyxin from 42% to 54%. Phospholipase D (cabbage) treatment significantly increased the La3+-displaceable Ca2+ to 0.227 +/- 0.02 nmol/microgram protein (P less than 0.05), a gain of 0.055 nmol. All of this phospholipid specific increment in bound Ca2+ was displaced by 0.1 mM Polymyxin B. The results suggest that Polymyxin B will be useful as a probe for phospholipid Ca2+-binding sites in natural membranes.
两亲性阳离子多粘菌素B已被证明能以剂量依赖性、饱和性方式从“气体解剖”的心肌肌膜中置换出Ca2+。在1 mM或10 mM Ca2+存在时，Ca2+置换仅部分可逆，分别为57%和63%。在最大置换浓度（1 mM）下，非特异性阳离子探针镧（La3+）置换的总Ca2+为0.172±0.02 nmol/μg膜蛋白。在0.1 mM时，多粘菌素B置换了总La3+可置换Ca2+的42%，即0.072±0.01 nmol/μg蛋白。5 mM多粘菌素置换的Ca2+量与1 mM La3+置换的量相等。用神经氨酸酶（去除唾液酸）和蛋白酶对膜进行预处理会导致La3+可置换Ca2+减少，但会使0.1 mM多粘菌素置换的比例从42%增加到54%。磷脂酶D（白菜）处理显著增加了La3+可置换Ca2+至0.227±0.02 nmol/μg蛋白（P<0.05），增加了0.055 nmol。所有这种结合Ca2+的磷脂特异性增加都被0.1 mM多粘菌素B置换。结果表明，多粘菌素B将作为天然膜中磷脂Ca2+结合位点的探针很有用。
