Structural studies of Caseinolytic protease 1 from Mycobacterium tuberculosis and Methionyl-tRNA synthetase from Mycobacterium smegmatis

Tuberculosis is a severe disease that causes about 2 million deaths every year. It is a worldwide threat and it is estimated that one-third of the world’s population carries the infection. The severe side effects of the present drugs, and the more than 6 months long treatment, in addition to the development of resistant bacterial strains, are the incentives for the intensified search for new drugs. In this work two potential mycobacterial drug targets have been studied: Caseinolytic protease 1 (ClpP1) from Mycobacterium tuberculosis (Mt) and Methionyl-tRNA synthetase (MetRS) from Mycobacterium smegmatis (Ms). The X-ray stucture of ClpP1 was determined to 3.0 Å resolution. The study gives details on the tetradecameric arrangement of the enzyme. Two hepameric discs assemble to form a chamber containing the catalytic activity mediated by each of the monomers. The chamber can be reached by two pores. Comparison with the human homologue reveals important structural differences. The X-ray studies on Ms MetRS were done to 2.3 Å and 2.8 Å resolution. The study gives details on the flexibility of the enzyme and how this is related to activity. Important findings are identification of an intermediate structure in which the methionine to be adenylated is bound in the catalytic site in a tight complex. The catalytic site and the anticodon recognizing domains are separated and the structural results indicate communication between the domains. The possibility to allosterically inhibit the enzyme is discussed