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Expression of the bacteriorhodopsin gene in Halobacterium halobium using a multicopy plasmid

Journal Article · · Proceedings of the National Academy of Sciences of the United States of America; (USA)
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  1. Massachusetts Institute of Technology, Cambridge (USA)
Bacteriorhodopsin (bR) was expressed in Halobacterium halobium by using a multicopy plasmid containing the bop gene. The plasmid contains pGRB1, a 1.8-kilobase-pair plasmid; a 70-base-pair fragment from ISH11, a recently characterized insertion sequence; and a 1.6-kilobase-pair fragment carrying the bop gene from H. halobium S9. When transformed with this plasmid, a bop- insertion mutant of H. halobium yielded purple (Pum+) colonies. The insertion at the chromosomal bop locus remained intact in transformed cells, indicating that the plasmid bop gene was responsible for the Pum+ phenotype. bR was induced in early stationary phase in both wild-type and transformed cells. The final level of bR in transformed cells was 25-40% of that in wild type. The lower level of expression was presumably due to plasmid instability. Purple membrane purified from transformed strains had absorption and visible CD properties similar to wild type and contained bR in a hexagonal lattice with the same unit-cell dimension as wild type. The structure of bR from wild-type and transformed strains was identical at a resolution of 7.2 A. When reconstituted into vesicles, the purple membrane from wild-type and transformed strains showed similar light-dependent proton-pumping activity.
OSTI ID:
5896075
Journal Information:
Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 88:3; ISSN PNASA; ISSN 0027-8424
Country of Publication:
United States
Language:
English