Electron microscope heteroduplex mapping of naphthalene oxidation genes on the NAH7 and SAL1 plasmids |
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Authors: | K M Yen M Sullivan I C Gunsalus |
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Affiliation: | 2. Department of Biochemistry, University of Illinois, Urbana, Illinois 61801, USA;1. Genex Corporation, 16020 Industrial Drive, Gaithersburg, Maryland 20877 USA |
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Abstract: | Introduction of the transposon Tn5 to serve as a marker allows electron microscope heteroduplex mapping of the naphthalene oxidation genes on the approximately 83-kb NAH7 and the related approximately 85-kb SAL1 plasmids. The electron microscope-mapped gene positions on the NAH7 plasmid are in close agreement with those mapped previously by restriction digestion. The SAL1 plasmid can be considered as a mutant NAH7 plasmid which fails to direct the conversion of naphthalene to salicylate because of a mutational block but retains intact coding sequences for salicylate oxidation. Analysis of heteroduplex molecules formed between the SAL1 and NAH7::Tn5 EcoRI fragments and the known NAH7/SAL1 homology strongly suggest that the SAL1 DNA is completely homologous to NAH7 DNA except that a approximately 2.5-kb DNA segment constituting most of the nahA gene is replaced by approximately 4.6-kb nonhomologous DNA. |
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