Spore-coat laccase CotA from Bacillus subtilis: crystallization and preliminary X-ray characterization by the MAD method.

Bacterial endospores are highly resistant structures that allow survival for long periods of time in adverse environments. The spore-forming Gram-positive bacterium Bacillus subtilis synthesizes a coat around the endospore during development composed of several assembled polypeptides. The role of these components of the spore coat remains unclear; however, some of them appear to be enzymes possibly involved in the assembly process or in the final properties of the spore. The outer spore-coat protein CotA is a 65 kDa polypeptide showing a high degree of sequence similarity with copper-dependent oxidases, including fungal and plant laccases, ascorbate oxidase and CueO from Esherichia coli. CotA has been recently characterized as a copper-dependent laccase. Unlike previously reported laccases, CotA shows increased thermostability. Here, the crystallization of a recombinant CotA protein produced in E. coli and the preliminary characterization of the crystals is reported. Structure solution by the MAD method at the copper K edge is also reported.