Identification of a γ-hexachlorocyclohexane dehydrochlorinase (LinA) variant with improved expression and solubility properties

Abstract

Under aerobic conditions, the enzyme γ-hexachlorocyclohexane dechlorinase (LinA) from Sphingomonas paucimobilis UT26 catalyses the elimination of chlorine atoms from the molecule of γ-hexachlorocyclohexane (γ-HCH) or lindane, a recalcitrant pesticide that is still widely used. In its native metabolic context, LinA starts the biodegradation process of lindane by transforming γ-HCH to 1,2,4 trichlorobenzene (TCB), a less persistent chemical. In an attempt to generate an improved version of this enzyme to be used in lindane bioremediation schemes, we have run an experimental evolution procedure on LinA, using Escherichia coli as the surrogate host. One round of random mutagenesis and subsequent screening for improved dechlorination in vivo sufficed to yield one mutant enzyme (LinAT10), bearing a single substitution C132R, that displayed a two-fold enhanced expression and three-fold enhanced solubility of the enzyme compared to the wild type protein. This resulted in a biological product with a six-fold increase in dechlorination ability when expressed in E. coli. The potential of this protein and its expression system for in situ bioremediation is discussed.

• Bioremediation
• dechlorinase
• in vitro evolution
• LinA
• lindane
• protein expression