/xypage/worksmart/tsp000/07ê9/5 Physical Structure and Expression of alkBA Encoding Alkane

The structural genes of the Pseudomonas maltophilia alk system, which are localized on the OCT plasmid were cloned as a 4.2-kilobase pair Hind III fragment. This fragment contains sequences for alkane hydroxylase gene (alkB) and rubredoxin reductase gene (alkA), respectively. The alkB gene encodes a 373-amino acid polypeptide (47.4 kD) that can be expressed at high levels in Pseudomonas and Esherichia coli. The alkBA genes were complemented with alkane hydroxylation in both bacteria. This result shows that alkBA gene is essential for alkane hydroxylation since chromosomal loci have been encoded for other enzymes involved in fatty acid oxidation. © 1996 Academic Press, Inc. Several strains of Pseudomonas are able to utilize n-alkanes as the sole carbon and energy source by virtue of the OCT plasmid-encoded alkane hydroxylase (1, 2). The gene clusters on the plasmid were found at the alkBAC operon that encodes for structural proteins and the alkR region that regulates positively their expression in the presence of an inducer, n-otane or dicyclopropylketon (3, 4, 5). The alkBAC operon contains the structural genes for membrane alkane hydroxylase (alkB), soluble rubredoxin reductase (alkA), and membrane alcohol dehydrogenase (alkC)(6). However, it is not essential that alkBAC operon codes for an alcohol dehydrogenase since this enzyme is als