Corrinoid activation by a RACE protein: studies on the interaction of the proteins involved.

The O-demethylases of anaerobes are corrinoid-dependent, ether-cleaving methyltransferase enzyme systems consisting of four components. The interaction of the O-demethylase components of the acetogenic bacterium Acetobacterium dehalogenans was studied by protein mobility on native PAGE, far-Western blot analysis and yeast two-hybrid screen. Using native PAGE and far-Western blot, the interaction of the activating enzyme (AE) with its substrate, the corrinoid protein (CP), could be observed. The interaction occurred with four different CPs of A. dehalogenans and a CP from Desulfitobacterium hafniense DCB-2, all involved in ether cleavage. In the corrinoid reduction assay, the AE reduced all CPs tested. This result indicates a broad substrate specificity of the AE of A. dehalogenans. In addition, an interaction of the A. dehalogenans CP of the vanillate-O-demethylase with the two methyltransferases of the same enzyme system was observed. The interaction of the ether-cleaving methyltransferase with the CP appeared to be significantly less pronounced than that reported for the homologous methanol and methylamine methyltransferase systems of methanogenic archaea.