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chloromuconolactone dehalogenase, Rhodococcus opacus 1CP
Abstract:
Chloroaromatic compounds are often very persistent environmental pollutants. Nevertheless, numerous bacteria are able to metabolize these compounds and to utilize them as sole energy and carbon sources. ıt Rhodococcus opacus} 1CP is able to degrade several chloroaromatic compounds, some of them {ıt via} a variation of the 3-chlorocatechol branch of the modified {ıt ortho}-cleavage pathway. This branch in {ıt R. opacus} differs from that in {ıt Proteobacteria} in the inability of the chloromuconate cycloisomerase to dehalogenate. Instead, a unique enzyme designated as chloromuconolactone dehalogenase (ClcF) is recruited. ClcF dehalogenates 5-chloromuconolactone to {ıt cis}-dienelactone and shows a high similarity to muconolactone isomerases (EC 5.3.3.4). However, unlike the latter enzymes, it is unable to catalyse the isomerization of muconolactone to 3-⁻oxoadipate enollactone. In order to characterize the catalytic mechanism of this unusual dehalogenase, the enzyme was crystallized and subjected to X-ray structural analysis. Data sets to up to 1.65Å resolution were collected from two different crystal forms using synchrotron radiation. Crystal form I (space group {ıt P}2{\sb 1}) contained 40 subunits in the asymmetric unit, whereas ten subunits were present in crystal form II (space group {ıt P}2{\sb 1}2{\sb 1}2{\sb 1). The self-rotation function revealed the orientations of the molecular symmetry axes of the homodecamer of 52 symmetry.
