Purification, crystallization and preliminary X-ray crystallographic studies of Rv3899c from Mycobacterium tuberculosis

Rv3899c, a hypothetical protein from Mycobacterium tuberculosis that is conserved within the mycobacteria, is predicted to be secreted and has been found in culture filtrates. Here, Rv3899c has been cloned, expressed in Escherichia coli and purified using standard chromatographic techniques. The hanging-drop vapour-diffusion method with PEG 3350 as a precipitant was used to crystallize the protein. N-terminal sequencing results showed that the amino-acid sequence of the crystallized protein began with GATAG, indicating that it is a fragment containing residues 184-410 of Rv3899c. Rv3899c(184-410) crystals exhibited the symmetry of space group P2(1)2(1)2(1), with unit-cell parameters a = 49.88, b = 54.72, c = 75.52 angstrom, = = = 90 degrees, and diffracted to a resolution of 1.90 angstrom.