THE ACTIVATION DOMAIN OF THE MOTA TRANSCRIPTION FACTOR FROM BACTERIOPHAGE-T4

Bacteriophage T4 encodes a transcription factor, MotA, that binds to t he -30 region of middle-mode promoters and activates transcription by host RNA polymerase. We have solved the structure of the MotA activati on domain to 2.2 Angstrom by X-ray crystallography, and have also dete rmined its secondary structure by NMR, An area on the surface of the p rotein has a distinctive patch that is populated with acidic and hydro phobic residues. Mutations within this patch cause a defective T4 grow th phenotype, arguing that the patch is important for MotA function, O ne of the mutant MotA activation domains was purified and analyzed by NMR, and the spectra clearly show that the domain is properly folded, The mutant full-length protein appears to bind DNA normally but is def icient in transcriptional activation, We conclude that the acidic/hydr ophobic surface patch is specifically involved in transcriptional acti vation, which is reminiscent of eukaryotic acidic activation domains.