Cloning, overexpression, purification and preliminary X-ray analysis of a Feast/famine regulatory protein (Rv2779c) from Mycobacterium tuberculosis H37Rv

Abstract

Rv2779c from M. tuberculosis is a Feast/Famine regulatory protein also known as Leucine responsive regulatory protein/Asparagine synthase C- family (Lrp/AsnC) of transcriptional regulators. This class of proteins is known to be involved in various metabolic processes of bacteria and fungi. They contain a RAM-domain (Regulator of Amino acid Metabolism) that is rarely found in humans and act as the oligomerisation domain. Since the oliogmeric status is often linked to the particular functional role in these proteins, binding of ligands to the domain can elicit specific functional responses. Full-length Rv2779c corresponding to a molecular weight of 19.8 kDa and 179 residues, was cloned and purified to homogeneity following transformation into E. coli C41 (DE3). Crystals were grown by vapour diffusion using the hanging drop method. Diffraction data extending to 2.8 Å resolution were collected from a single crystal with unit cell parameters a = 99.6 Å, b = 146.0 Å, c= 49.9 Å and space group P21212. Matthews coefficient (Vm) calculations suggests that 4 molecules are present in the asymmetric unit corresponding to a solvent content of ~46%. Molecular-replacement calculations using the crystal structure of a homolog, Rv3291c, as the search model gave an unambiguous solution corresponding to 4 subunits in the asymmetric unit.