Biological roles of two new murein hydrolases of Streptococcus pneumoniae representing examples of module shuffling.

We have found two murein hydrolases (LytB and LytC) tightly bound to the cell envelope that have completely changed the domain building plan previously reported for the murein hydrolases of Streptococcus pneumoniae. The active center of LytB and LytC is located at the C-terminal, whereas the binding domain is at the N-terminal. LytC has been characterized as the first lysozyme of S. pneumoniae and behaves as an autolysin at 30 degrees C. LytB appears as the main hydrolase responsible for cell separation since inactivation of lytB leads to the formation of long chains of more than 100 cells. These findings indicate that genetic adaptation of mobile domains is extremely efficient in pneumococcus.