title: Structure of Haemophilus influenzae HslV protein at 1.9 A resolution, revealing a cation-binding site near the catalytic site.
abstract: The structure of the Haemophilus influenzae HslV protease of the HslUV 'prokaryotic proteasome' has been solved by molecular replacement and refined with data to 1.9 A resolution. The protease is a 'double donut' of hexameric rings; two alternative sets of intermolecular interactions between protomers in the rings result in 'quasi-equivalent' packing within the assembly. Anomalous scattering data from crystals with potassium present in the mother liquor reveal a K(+) ion bound with octahedral coordination near the active-site Thr1 residue. The site also binds Na(+) ions and is likely to bind Mg(2+), suggesting that monovalent and divalent metal ions may influence the catalytic activity of the protease.
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA. dave.mckay@stanford.edu
authors.forename: M C
authors.initials: MC
authors.lastname: Sousa
authors.forename: D B
authors.initials: DB
authors.lastname: McKay
mesh_terms: D049069:ATP-Dependent Proteases; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D002412:Cations / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D010450:Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D006193:Haemophilus influenzae / Q000737:chemistry* / Q000201:enzymology; D006360:Heat-Shock Proteins; D006868:Hydrolysis; D008958:Models, Molecular; D011487:Protein Conformation; D012697:Serine Endopeptidases
chemical_list: D002412:Cations; D006360:Heat-Shock Proteins; D010450:Endopeptidases; D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; D000251:Adenosine Triphosphatases