Crystallization and preliminary X-ray diffraction studies on the N-utilizing substance A (NusA) from Mycobacterium tuberculosis

N-utilizing substance A (NusA) is a protein which performs several roles as a cofactor of DNA-dependent RNA polymerase. Its acts as an elongation factor and facilitates pausing, termination and the formation of a complex assembly that mediates transcription antitermination in eubacteria. Biochemical and biophysical data in the literature suggest that this protein performs these functions by binding to the core RNA polymerase, other protein factors and certain RNA fragments having specific signal sequences. The NusA of Mycobacterium tuberculosis has been cloned and overexpressed in Escherichia coli and crystallized using the hanging-drop vapour-diffusion method. The space group is P3₁21, with unit-cell parameters a = b = 78.1, c = 180.3 Å. A native data set complete to 1.7 Å resolution has been collected from a single crystal.