The high-resolution structure of DNA-binding protein HU from Bacillus stearothermophilus

Protein HU is a ubiquitous prokaryotic protein which controls the architect ure of genomic DNA. It binds DNA non-specifically and promotes the bending and supercoiling of the double helical structure. HU is involved in many DN A-associated cellular processes, including replication, transcription and t he packaging of DNA into chromosome-like structures. Originally determined at medium resolution, the crystal structure of HU has now been refined at 2 .0 Angstrom resolution. The high-resolution structure shows that the dimeri c molecule is essentially a compact platform for two flexible and basic arm s which wrap around the DNA molecule. To maximize the protein's stability, non-secondary structural regions are reduced to a minimum, there is an exte nsive aromatic hydrophobic core and several salt bridges and hydrogen-bonde d water molecules knit together crucial regions, Based on the original medi um-resolution structure of HU, several proposals were made concerning the s tructural basis of HU's ability to bind, bend and supercoil DNA. Each of th ese proposals is fully supported by the high-resolution structure, Most not ably, the surfaces of the molecule which appear to mediate protein-DNA and protein-protein interactions have the ideal shapes and physicochemical prop erties to perform these functions.