CRYSTAL-STRUCTURE OF THE OCT-1 POU DOMAIN BOUND TO AN OCTAMER SITE - DNA RECOGNITION WITH TETHERED DNA-BINDING MODULES

The structure of an Oct-1 POU domain-octamer DNA complex has been solv ed at 3.0 Angstrom resolution. The POU-specific domain contacts the 5' half of this site (ATG- CAAAT), and as predicted from nuclear magneti c resonance studies, the structure, docking, and contacts are remarkab ly similar to those of the lambda and 434 repressors. The POU homeodom ain contacts the 3' half of this site (ATGCAAAT), and the docking is s imilar to that of the engrailed, MAT alpha 2, and Antennapedia homeodo mains. The linker region is not visible and there are no protein-prote in contacts between the domains, but overlapping phosphate contacts ne ar the center of the octamer site may favor cooperative binding. This novel arrangement raises important questions about cooperativity in pr otein-DNA recognition.