t a resolution of 35 angstroms, the 3-D images identify critical components
of these "transcriptional factor" or TF proteins, including TFIID, TFIIA
and TFIIB. A model reconstructed from the images shows TFIID as a horseshoe-shaped
structure surrounding a central cavity inside of which recognition and
binding to dna takes place. TFIIA and TFIIB are shown to bind to the TFIID
in a way that affects the size and shape of the cavity.