 |
The
first structure of a pneumococcal
autolysin, that of LytC, has been solved in ternary complex with
choline and a pneumococcal peptidoglycan fragment. The active site of
the hydrolase module is not fully exposed but oriented towards the
choline-binding module accounting for its unique in vivo features in
peptidoglycan hydrolysis, its activation and its regulatory mechanisms.
Due to the unusual hook-shaped conformation of the multimodular
protein, it is only able to hydrolyze non-crosslinked peptidoglycan
chains, an assertion validated by additional experiments. These results
explain the activation of LytC by CbpD in fratricide, a
competence-programmed mechanism of predation of noncompetent sister
cells. The results provide the first structural insights into the
critical and central function that LytC plays in pneumococcal virulence
and explain a long-standing puzzle of how murein hydrolases can be
controlled to avoid self-lysis during bacterial growth and division. References: Pérez-Dorado, I; González, A; Morales, M; Sanles, R; Striker, W; Vollmer, W; Mobashery, S; García, JL; Martínez-Ripoll, M; García, P; Hermoso, JA Nature Structural & Molecular Biology (2010) 17, 576-582 (doi:10.1038/nsmb.1817) Enjoy the short movie shown below, explaining how CbpD activates LytC in fratricide... |