Structure-function studies on bacteriorhodopsin. II. Improved expression of the bacterio-opsin gene in Escherichia coli.
Structure-function studies on bacteriorhodopsin. II. Improved expression of the bacterio-opsin gene in Escherichia coli.
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DOI：
10.1016/s0021-9258(18)48074-x
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发表时间：
1987-07
期刊：
影响因子：
--
通讯作者：
S. Karnik;M. Nassal;T. Doi;E. Jay;V. Sgaramella;H. Khorana
中科院分区：
文献类型：
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作者：
S. Karnik;M. Nassal;T. Doi;E. Jay;V. Sgaramella;H. Khorana
The aims of this work have been to express bacterio-opsin with minimal variation from the native primary structure and to improve the level of expression in Escherichia coli. We describe the construction of plasmids in which the bacterio-opsin gene contains only an additional methionine residue at the N terminus and in which the C-terminal aspartic acid encoded in the gene has been deleted to conform to the mature protein. In attempts to improve bacterio-opsin expression, a variety of expression plasmids were constructed in which the promoters and the ribosome-binding sequences were varied. Invariably, in these plasmids, translation but not transcription of the bacterio-opsin gene was limiting. A striking increase in expression of the gene occurred when the codons for several of the N-terminal amino acids were changed to increase the A = T content. Bacterio-opsin expressed in E. coli was degraded with a half-life of 8-10 min. The addition of hydrophobic signal sequences at the N terminus increased the half-life and overall yield of the protein. Bacterio-opsin thus produced regenerated the native bacteriorhodopsin-like chromophore and carried out light-dependent proton translocation at a rate comparable to that of the native bacterio-opsin prepared from the purple membrane.
