THE PLASMID-LOCATED HALOALKANE DEHALOGENASE GENE FROM RHODOCOCCUS-RHODOCHROUS NCIMB-13064

The haloalkane dehalogenase (dhaA) gene from Rhodococcus rhodochrous N CIMB 13064 was cloned and sequenced. Its comparison with the previousl y studied dhlA gene from Xanthobacter autotrophicus GJ10 did not show homology. However, the amino acid sequences of the products of these g enes showed approximately 30% identity and several of the catalytic am ino acid residues were conserved in the NCIMB 13064 dehalogenase. A hi gh level of dhaA expression was demonstrated in Escherichia coil cells and this gene was shown to encode a dehalogenase with the activity ag ainst chloroalkanes of chain length C-3-C-10. Also, some dehalogenase activity against 1,2-dichloroethane encoded by the cloned dhaA gene wa s detected. The analysis of NCIMB 13064 derivatives lacking dehalogena se activity showed that the dhaA gene was located on the 100 kbp pRTL1 plasmid. It was also found that reversible rearrangements of DNA in t he dhaA region may be responsible for the control of expression of hal oalkane dehalogenase in R. rhodochrous NCIMB 13064. A number of repeat ed and inverted sequences which may cause genetic instability at the l ocus were found in the haloalkane dehalogenase gene region.