title: Crystal structure of HslUV complexed with a vinyl sulfone inhibitor: corroboration of a proposed mechanism of allosteric activation of HslV by HslU.
abstract: On the basis of the structure of a HslUV complex, a mechanism of allosteric activation of the HslV protease, wherein binding of the HslU chaperone propagates a conformational change to the active site cleft of the protease, has been proposed. Here, the 3.1 A X-ray crystallographic structure of Haemophilus influenzae HslUV complexed with a vinyl sulfone inhibitor is described. The inhibitor, which reacts to form a covalent linkage to Thr1 of HslV, binds in an "antiparallel beta" manner, with hydrogen-bond interactions between the peptide backbone of the protease and that of the inhibitor, and with two leucinyl side chains of the inhibitor binding in the S1 and S3 specificity pockets of the protease. Comparison of the structure of the HslUV-inhibitor complex with that of HslV without inhibitor and in the absence of HslU reveals that backbone interactions would correctly position a substrate for cleavage in the HslUV complex, but not in the HslV protease alone, corroborating the proposed mechanism of allosteric activation. This activation mechanism differs from that of the eukaryotic proteasome, for which binding of activators opens a gated channel that controls access of substrates to the protease, but does not perturb the active site environment.
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Sherman Fairchild Building, Stanford, CA 94305-5400, USA.
authors.forename: Marcelo C
authors.initials: MC
authors.lastname: Sousa
authors.forename: Benedikt M
authors.initials: BM
authors.lastname: Kessler
authors.forename: Herman S
authors.initials: HS
authors.lastname: Overkleeft
authors.forename: David B
authors.initials: DB
authors.lastname: McKay
mesh_terms: D049069:ATP-Dependent Proteases; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000494:Allosteric Regulation; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D004789:Enzyme Activation; D006193:Haemophilus influenzae / Q000201:enzymology; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D011480:Protease Inhibitors / Q000737:chemistry; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D013450:Sulfones / Q000737:chemistry
chemical_list: D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D013450:Sulfones; C009873:divinyl sulfone; D010450:Endopeptidases; D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases