Structural studies of a yeast quaternary transcription-initiation complex

A 96.7 kDa quaternary transcription-factor complex consisting of the conserved core domains of yeast TBP, TFIIA, TFIIB and TATA-box DNA has been assembled from purified components. Crystals of the complex were obtained by the hanging-drop vapor-diffusion method. Native data sets were collected at synchrotron sources. Crystal form I belongs to space group R32, with unit-cell parameters a = b = 173.2, c = 164.1 Å, and diffracts to 2.5 Å resolution, but contains substoichiometric amounts of TFIIB. Crystal form II was assembled with a longer piece of DNA than that used for form I crystals and contains the complete quaternary complex. These crystals belong to space group P42₁2, with unit-cell parameters a = b = 141.7, c = 112.0 Å, and diffract to 3.6 Å resolution.