α-乳白蛋白与膜的结合：部分埋藏蛋白的证据。

Alpha-lactalbumin binding to membranes: evidence for a partially buried protein.

作者信息

Berliner L J, Koga K

出版信息

Biochemistry. 1987 Jun 2;26(11):3006-9. doi: 10.1021/bi00385a008.

Abstract

The self-incorporation of apo-alpha-lactalbumin (alpha-LA) into single unilamellar vesicles (SUV) of dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine was demonstrated by column chromatographic analyses on Sephadex G-200 (10 mM Tris-HCl, pH 7.4, 26-28 degrees C) and by intrinsic fluorescence emission of SUV-bound alpha-LA. It was shown that apo-alpha-LA slowly incorporated into the DMPC vesicle bilayer after equilibrating different mixtures of protein and SUV for several hours. The intrinsic fluorescence properties of the bound apo-alpha-LA were altered only slightly (lambda maxem = 333 nm vs. 337 nm in aqueous solution). The large blue shift in apo-alpha-LA fluorescence in solution induced by monovalent cations, such as Na(I), was almost completely prevented when apo-alpha-LA was membrane bound. Furthermore, the addition of calcium caused a slow conversion from apo-alpha-LA to Ca(II)-alpha-LA by a mechanism consistent with passive diffusion of Ca(II) into the bilayer interior to the (buried) calcium binding site. The release of Ca(II)-alpha-LA from the membrane is discussed with reference to alpha-LA release from the smooth endoplasmic reticulum in vivo.

摘要

通过在Sephadex G - 200（10 mM Tris - HCl，pH 7.4，26 - 28℃）上的柱色谱分析以及与单室脂质体（SUV）结合的脱辅基α-乳白蛋白（α-LA）的固有荧光发射，证明了脱辅基α-乳白蛋白（α-LA）自掺入二肉豆蔻酰磷脂酰胆碱（DMPC）和二棕榈酰磷脂酰胆碱的单室脂质体（SUV）中。结果表明，在将蛋白质和SUV的不同混合物平衡数小时后，脱辅基α-LA缓慢掺入DMPC囊泡双层中。结合的脱辅基α-LA的固有荧光特性仅略有改变（最大发射波长λmaxem = 333 nm，而在水溶液中为337 nm）。当脱辅基α-LA与膜结合时，由单价阳离子如Na（I）诱导的溶液中脱辅基α-LA荧光的大蓝移几乎完全被阻止。此外，钙的添加通过与Ca（II）被动扩散到双层内部至（埋藏的）钙结合位点相一致的机制，导致脱辅基α-LA缓慢转化为Ca（II）-α-LA。参考体内α-LA从滑面内质网的释放，讨论了Ca（II）-α-LA从膜中的释放。