The MotA Protein from Bacteriophage T4 Contains Two Domains: Preliminary Structural Analysis by X-ray Diffraction and Nuclear Magnetic Resonance

Abstract Controlled protease cleavage experiments and N-terminal sequence analyses were used to show that the transcriptional activator MotA from bacteriophage T4 has a two-domain structure. The N and C-terminal domains have M r values of 10,300 and 11,800, respectively, and were separately cloned and overexpressed in Escherichia coli . One and two-dimensional NMR spectroscopy indicate that both domains have stably folded structures and contain extensive secondary structure. The N-terminal domain is substantially α-helical, whereas the C-terminal domain has a high content of β-strand. The N-terminal domain has been crystallized under three different conditions, all with the space group P 3 1(2) 21 and similar unit cell dimensions. The best crystals are grown from ammonium sulfate, have cell dimensions a = b = 46·7 A, c = 139·6 A, and diffract to beyond 2·4 A. The high quality of the NMR and diffraction data will allow a complete structural analysis of MotA by a combination of these techniques.