Tozuka M, Fidge N
Baker Medical Research Institute, Prahran, Melbourne, Victoria, Australia.
Biochem J. 1989 Jul 1;261(1):239-44. doi: 10.1042/bj2610239.
The liver plays a major role in the metabolism of plasma high-density lipoprotein (HDL). Several groups have postulated, but others refuted, the existence of a classical membrane receptor which recognizes HDL. In the present study, we identified and purified two liver HDL-binding proteins of 120 kDa (HB1) and 100 kDa (HB2), with apparent specificity for HDL3 devoid of E apolipoprotein. The plasma membrane was the richest source of the HDL-binding protein. Both proteins bound A-I and A-II apolipoproteins and retained HDL-binding activity after final purification. HB1 activity, but not that of HB2, was lost after treatment with beta-mercaptoethanol, but reduction did not change the apparent molecular mass of either protein. Antibodies against HB1 or HB2 did not cross-react, and preliminary structural investigations provide evidence to suggest that HB1 and HB2 are not structurally related. We thus provide evidence for at least two liver plasma-membrane proteins which bind HDL apolipoproteins, suggesting that protein-protein interaction participates to some degree in the mechanism of HDL recognition by cells.
肝脏在血浆高密度脂蛋白（HDL）的代谢中起主要作用。几个研究小组曾推测存在一种识别HDL的经典膜受体，但其他小组予以反驳。在本研究中，我们鉴定并纯化了两种肝脏HDL结合蛋白，分子量分别为120 kDa（HB1）和100 kDa（HB2），它们对不含E载脂蛋白的HDL3具有明显的特异性。质膜是HDL结合蛋白最丰富的来源。两种蛋白都能结合A-I和A-II载脂蛋白，并且在最终纯化后仍保留HDL结合活性。用β-巯基乙醇处理后，HB1的活性丧失，但HB2的活性未丧失，不过还原作用并未改变两种蛋白的表观分子量。针对HB1或HB2的抗体不发生交叉反应，初步结构研究提供的证据表明HB1和HB2在结构上不相关。因此，我们提供了证据，证明至少有两种肝脏质膜蛋白能结合HDL载脂蛋白，这表明蛋白质-蛋白质相互作用在某种程度上参与了细胞识别HDL的机制。
