[Lytic enzymes of the pneumococcal system]

Abstract

The cell wall lytic enzymes of Streptococcus pneumoniae and its bacteriophages provide a reliable experimental model to support the extended idea concerning the modular organization of most proteins. The comparative analysis of the deduced amino acid sequences of these enzymes, as well as the construction of functional chimeric phage-bacterial enzymes, demonstrate that the C-terminal domain, which contains a large number of repeated amino acid motifs, is the substrate-binding domain, whereas the N-terminal domain provides enzymatic specificity. The development of chimeric proteins from genes encoding enzymes that specifically degrade cell wall of bacteria belonging to different genera (e.g. Streptococcus and Clostridium), supports the hypothesis concerning domainal interchange as a driving force for the construction of novel functional proteins that bacteria might create to allow them to become adapted to new environmental situations.