Takemoto L J, Hansen J S, Nicholson B J, Hunkapiller M, Revel J P, Horwitz J
Biochim Biophys Acta. 1983 Jun 10;731(2):267-74. doi: 10.1016/0005-2736(83)90018-4.
A protein of Mr 26000 has been shown to be the major component of eye-lens junctions, which are similar but not identical to the gap junctions of liver and other tissues. Cyanogen bromide cleavage of the Mr 26000 polypeptide from bovine lenses yields a major fragment of Mr 15000 (fragment 1). However, if the junctions are first treated with trypsin or carboxypeptidase Y, cyanogen bromide treatment yields a fragment of reduced molecular weight. Since protease treatment has been shown to cleave residues almost exclusively from the carboxy-terminal end of the Mr 26000 polypeptide, it follows that fragment 1 represents the carboxy-terminal half of this molecule, part of which is exposed to proteolytic attack outside the membrane. This latter result is corroborated by the fact that antisera which recognize both the Mr 26000 polypeptide and fragment 1 fail to do so after preadsorption with intact membranes. In addition, comparative amino acid and partial sequence analyses of the Mr 26000 polypeptide and fragment 1 indicate that fragment 1 is more hydrophilic in character, suggesting that much of the amino-terminal half of the Mr 26000 polypeptide is buried within the lipid bilayer.
一种分子量为26000的蛋白质已被证明是眼晶状体连接的主要成分，它与肝脏及其他组织的间隙连接相似但并不完全相同。用溴化氰裂解牛晶状体中分子量为26000的多肽可产生一个主要片段，分子量为15000（片段1）。然而，如果先将连接用胰蛋白酶或羧肽酶Y处理，再用溴化氰处理，则会产生分子量降低的片段。由于蛋白酶处理已被证明几乎只从分子量为26000的多肽的羧基末端切割残基，因此片段1代表该分子的羧基末端一半，其中一部分在膜外易受蛋白水解攻击。后一结果得到以下事实的证实：识别分子量为26000的多肽和片段1的抗血清在用完整膜预吸附后不再能识别。此外，对分子量为26000的多肽和片段1的氨基酸比较分析及部分序列分析表明，片段1在性质上更具亲水性，这表明分子量为26000的多肽的氨基末端一半的大部分埋藏在脂质双层内。
