Targeting the Cell Wall of Mycobacterium tuberculosis: Structure and Mechanism of L,D-Transpeptidase 2

Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Structure (Impact Factor: 6.79). 10/2012; 20(12). DOI: 10.1016/j.str.2012.09.016
Source: PubMed

ABSTRACT With multidrug-resistant cases of tuberculosis increasing globally, better antibiotic drugs and novel drug targets are becoming an urgent need. Traditional β-lactam antibiotics that inhibit D,D-transpeptidases are not effective against mycobacteria, in part because mycobacteria rely mostly on L,D-transpeptidases for biosynthesis and maintenance of their peptidoglycan layer. This reliance plays a major role in drug resistance and persistence of Mycobacterium tuberculosis (Mtb) infections. The crystal structure at 1.7 Å resolution of the Mtb L,D-transpeptidase Ldt(Mt2) containing a bound peptidoglycan fragment, reported here, provides information about catalytic site organization as well as substrate recognition by the enzyme. Based on our structural, kinetic, and calorimetric data, we propose a catalytic mechanism for Ldt(Mt2) in which both acyl-acceptor and acyl-donor substrates reach the catalytic site from the same, rather than different, entrances. Together, this information provides vital insights to facilitate development of drugs targeting this validated yet unexploited enzyme.

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