The MotA protein from bacteriophage T4 contains two domains. Preliminary structural analysis by X-ray diffraction and nuclear magnetic resonance.

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 alpha-helical, whereas the C-terminal domain has a high content of beta-strand. The N-terminal domain has been crystallized under three different conditions, all with the space group P3(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.