Bradshaw R A, Ericsson L H, Walsh K A, Neurath H
Proc Natl Acad Sci U S A. 1969 Aug;63(4):1389-94. doi: 10.1073/pnas.63.4.1389.
The amino acid sequence of the four fragments produced by treatment of bovine carboxypeptidase A with cyanogen bromide has been completed. The alignment of these fragments, previously established by peptic digest of the whole protein, allows for the description of the complete primary structure of the molecule. A comparison of the proposed functional residues, identified by X-ray diffraction analyses, has either confirmed their assignments or provided their correct identity. The functional and structural residues of principal importance include Arg 145, Tyr 248, and Glu 270 as the binding site of the substrate carboxyl group, the proton donor, and the nucleophilic moiety, respectively, which were correctly assigned; His 196 as the third zinc ligand and Tyr 265 as the binding site of the alpha-carboxyl group have been corrected from their original X-ray assignments. The other two zinc ligands, His 69 and Glu 72, were identified previously from chemical and X-ray studies. The assignment of the two half-cystinyl residues and the postulation of the existence of a disulfide bond have been confirmed.
用溴化氰处理牛羧肽酶A产生的四个片段的氨基酸序列已完成。这些片段的排列，此前通过对整个蛋白质的胃蛋白酶消化确定，使得能够描述该分子的完整一级结构。通过X射线衍射分析鉴定的拟议功能残基的比较，要么证实了它们的归属，要么提供了它们的正确身份。主要重要的功能和结构残基包括分别作为底物羧基、质子供体和亲核部分的结合位点的精氨酸145、酪氨酸248和谷氨酸270，它们的归属正确；组氨酸196作为第三个锌配体，酪氨酸265作为α-羧基的结合位点，已从其最初的X射线归属中得到校正。另外两个锌配体，组氨酸69和谷氨酸72，先前已从化学和X射线研究中鉴定出来。两个半胱氨酰残基的归属以及二硫键存在的假设已得到证实。
