Search tips
Search criteria 


Logo of narLink to Publisher's site
Nucleic Acids Res. 1994 March 25; 22(6): 1068–1074.
PMCID: PMC307931

Direct selection of binding proficient/catalytic deficient variants of BamHI endonuclease.


Variants of BamHI endonuclease in which the glutamate 113 residue has been changed to lysine or the aspartate 94 to asparagine were shown to behave as repressor molecules in vivo. This was demonstrated by placing a BamHI recognition sequence, GGATCC, positioned as an operator sequence in an antisense promoter for the aadA gene (spectinomycin resistance). Repression of this promoter relieved the inhibition of expression of spectinomycin resistance. This system was then used to select new binding proficient/cleavage deficient BamHI variants. The BamHI endonuclease gene was mutagenized either by exposure to hydroxylamine or by PCR. The mutagenized DNA was reintroduced into E. coli carrying the aadA gene construct, and transformants that conferred spectinomycin resistance were selected. Twenty Spr transformants were sequenced. Thirteen of these were newly isolated variants of the previously identified D94 and E113 residues which are known to be involved in catalysis. The remaining seven variants were all located at residue 111 and the glutamate 111 residue was shown to be involved with catalysis.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.4M), or click on a page image below to browse page by page.

Images in this article

Click on the image to see a larger version.

Articles from Nucleic Acids Research are provided here courtesy of Oxford University Press