Pseudomonas paucimobilis UT26 grows on γ-hexachlorocyclohexane (γ-HCH) as a sole source of carbon and energy. Tn5 mutation was introduced into UT26, and two kinds of mutants defective in γ-HCH degradation were phenotypically isolated; one (UT64) completely lacked the activity to degrade γ-HCH, while the other (UT61) retained a very low level of activity. Tagging and sequencing analysis showed that both mutants had a Tn5 insertion at the same site of the linA (γ-HCH dehydrochlorinase encoding) gene. However, UT61 had an additional rearrangement, which could be the cause of its retaining a low level of activity. An in vitro complementation test with a crude extract from UT64 plus partially purified LinA protein showed that LinA was essential not only for the first-step reaction (γ-HCH to γ-pentachlorocyclohexene; γ-PCCH), but also for the second-step reaction (γ-PCCH to compound B) of γ-HCH degradation in UT26.
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