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 fact or and facilitates pausing, termination and the formation of a complex asse mbly 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 factor s and certain RNA fragments having specific signal sequences. The NusA of M ycobacterium tuberculosis has been cloned and overexpressed in Escherichia coli and crystallized using the hanging-drop vapour-diffusion method. The s pace group is P3(1)21, with unit-cell parameters a = b = 78.1, c = 180.3 An gstrom. A native data set complete to 1.7 Angstrom resolution has been coll ected from a single crystal.