title: Crystal structure of the protease domain of a heat-shock protein HtrA from Thermotoga maritima.
abstract: HtrA (high temperature requirement A), a periplasmic heat-shock protein, functions as a molecular chaperone at low temperatures, and its proteolytic activity is turned on at elevated temperatures. To investigate the mechanism of functional switch to protease, we determined the crystal structure of the NH(2)-terminal protease domain (PD) of HtrA from Thermotoga maritima, which was shown to retain both proteolytic and chaperone-like activities. Three subunits of HtrA PD compose a trimer, and multimerization architecture is similar to that found in the crystal structures of intact HtrA hexamer from Escherichia coli and human HtrA2 trimer. HtrA PD shares the same fold with chymotrypsin-like serine proteases, but it contains an additional lid that blocks access the of substrates to the active site. A corresponding lid found in E. coli HtrA is a long loop that also blocks the active site of another subunit. These results suggest that the activation of the proteolytic function of HtrA at elevated temperatures might occur by a conformational change, which includes the opening of the helical lid to expose the active site and subsequent rearrangement of a catalytic triad and an oxyanion hole.
authors.affiliation: Department of Molecular Cell Biology, Center for Molecular Medicine, SBRI, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
authors.forename: Dong Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Dong Ryoung
authors.initials: DR
authors.lastname: Kim
authors.forename: Sung Chul
authors.initials: SC
authors.lastname: Ha
authors.forename: Neratur K
authors.initials: NK
authors.lastname: Lokanath
authors.forename: Chang Jun
authors.initials: CJ
authors.lastname: Lee
authors.forename: Hye-Yeon
authors.initials: HY
authors.lastname: Hwang
authors.forename: Kyeong Kyu
authors.initials: KK
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D033903:Periplasmic Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D020124:Thermotoga maritima / Q000201:enzymology*
chemical_list: D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; C061682:DegP protease; D012697:Serine Endopeptidases