Thatcher D R
Biochem J. 1975 May;147(2):313-26. doi: 10.1042/bj1470313.
The chemical structure of the extracellular beta-lactamase I of Bacillus cereus 569/H was investigated. Three electrophoretically homogenous charge variants of this enzyme were isolated and amino acid analysis of each revealed no significant differences. However, a degree of N-terminal heterogeneity was found by direct end-group modification of the protein and also on alignment of peptides from tryptic and chymotryptic digestion. The N-terminal heterogeneity observed was great enough to explain the production of the beta-lactamase I isoenzymes which are probably produced by postsynthesis modification of a single gene product. Over 80% of the amino acid sequence of beta-lactamase I was determined by the detailed analysis of peptides derived from tryptic, chymotryptic and thermolytic digests. Five polypeptide fragments were constructed from these data and aligned by comparison with the known amino acid sequences of the penicillinases produced by Bacillus licheniformis and Staphylococcus aureus (Ambler & Meadway, 1969). About 60% of the proposed sequence was identical with that of B. licheniformis penicillinase, whereas the S. aureus enzyme had only about 40% of its residues in common with beta-lactamase I. These results are discussed with reference to the possible evolutionary relationships existing between known beta-lactamases. Detailed evidence for the amino acid sequence proposed has been deposited as Supplementary Publication SUP 50044 (27 pages) at the British Library (Lending Division), Boston Spa, Wetherby, W. Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1975), 145, 5.
对蜡样芽孢杆菌569/H的细胞外β-内酰胺酶I的化学结构进行了研究。分离出了该酶的三种电泳均一的电荷变体，对每种变体的氨基酸分析均未发现显著差异。然而，通过蛋白质的直接末端基团修饰以及胰蛋白酶和糜蛋白酶消化产生的肽段比对，发现了一定程度的N端异质性。观察到的N端异质性足以解释β-内酰胺酶I同工酶的产生，这些同工酶可能是由单一基因产物的合成后修饰产生的。通过对胰蛋白酶、糜蛋白酶和嗜热菌蛋白酶消化产生的肽段进行详细分析，确定了β-内酰胺酶I超过80%的氨基酸序列。根据这些数据构建了五个多肽片段，并与地衣芽孢杆菌和金黄色葡萄球菌产生的青霉素酶的已知氨基酸序列进行比对（安布勒和米德韦，1969年）。约60%的推测序列与地衣芽孢杆菌青霉素酶的序列相同，而金黄色葡萄球菌的酶与β-内酰胺酶I只有约40%的残基相同。结合已知β-内酰胺酶之间可能存在的进化关系对这些结果进行了讨论。所提出的氨基酸序列的详细证据已作为补充出版物SUP 50044（27页）存放在英国图书馆（借阅部），地址为英国西约克郡韦瑟比波士顿温泉LS23 7BQ，可按《生物化学杂志》（1975年）第145卷第5期所示条件从该处获取复印件。
