The ether-cleaving methyltransferase of the strict anaerobe Acetobacterium dehalogenans: Analysis of the zinc-binding site

Abstract

The anaerobic phenyl methyl ether cleavage in acetogenic bacteria is mediated by multicomponent enzyme systems designated O-demethylases. Depending on the growth substrate, different O-demethylases are induced in Acetobacterium dehalogenans. A vanillate- and a veratrol-O-demethylase of this organism have been described earlier. The methyltransferase I (MT I), a component of this enzyme system, catalyzes the ether cleavage and the transfer of the methyl group to a super-reduced corrinoid bound to a protein. The MT I of the vanillate- and veratrol-O-demethylase (MT Ivan and MT Iver) were found to be zinc-containing enzymes. By site-directed mutagenesis, putative zinc ligands were identified, from which the following unique zinc-binding motifs were derived: E-X14-E-X20-H for MT Ivan and D-X27-C-X39-C for MT Iver. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd.