期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：6
页码：3501-3505
DOI：10.1073/pnas.78.6.3501
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The penicillinase of Bacillus licheniformis is shown to be secreted cotranslationally. In extracts it was formed by membrane-associated but not by free polysomes; and after extracellular labeling of cells, followed by completion of the growing chains on polysomes in vitro, labeled penicillinase could be immunoprecipitated. This product contained electrophoretic peaks of Mr 36,000, 33,000, and 29,000, which correspond to previously reported forms of the enzyme. The Mr 36,000 form exhibits moderate hydrophobicity, as expected of a precursor with an NH2-terminal signal sequence for secretion. In addition, part of the Mr 33,000 fraction evidently contains a lipid: it is even more hydrophobic, and [2-3H]glycerol was found to be incorporated into these molecules but not into the other forms of the enzyme. These findings renew the earlier, discarded suggestion that the Mr 33,000 membrane-bound penicillinase in the cells contains lipid. The incorporation of lipid and two different cleavages can evidently all occur during growth of the penicillinase chain. Moreover, the resulting terminal regions are all accessible to extracellular labeling on growing chains. Several additional, unidentified lipoproteins also incorporate lipid during chain growth.
