Role of the C-terminal domain of the lysozyme of Clostridium acetobutylicum ATCC 824 in a chimeric pneumococcal-clostridial cell wall lytic enzyme.

An active chimeric cell wall lytic enzyme has been constructed by domain substitution between the major autolysins of Clostridium acetobutylicum ATCC 824 and Streptococcus pneumoniae. The chimeric enzyme, built up by the fusion of the N-terminal domain of the pneumococcal LYTA amidase and the C-terminal domain of the clostridial LYC lysozyme, exhibited an amidase activity capable of hydrolyzing choline-containing clostridial cell walls with an efficiency 250-times higher than when tested on pneumococcal cell walls. This experimental approach demonstrates the basic role of the C-terminal domain of the LYC lysozyme in substrate recognition and provides additional support to our hypothesis of modular evolution of these lytic enzymes. Moreover, the construction described here confirmed the role of the C-terminal domains of the modular cell wall lytic enzymes on the optimal pH for catalytic activity. To our knowledge, this is the first example of the construction of an active chimeric lytic enzyme by fusing genes that lack nucleotide homology and are derived from different bacterial genera.