1DBI

CRYSTAL STRUCTURE OF A THERMOSTABLE SERINE PROTEASE

Summary for 1DBI

• Entry DOI: 10.2210/pdb1dbi/pdb
• Descriptor: AK.1 SERINE PROTEASE, CALCIUM ION, SODIUM ION, ... (4 entities in total)
• Functional Keywords: hydrolase
• Biological source: Bacillus sp. AK1
• Cellular location: Secreted: Q45670
• Total number of polymer chains: 1
• Total formula weight: 29932.62

Authors

Smith, C.A.,Toogood, H.S.,Baker, H.M.,Daniel, R.M.,Baker, E.N. (deposition date: 1999-11-02, release date: 1999-11-18, Last modification date: 2024-10-30)

Primary citation

Smith, C.A.,Toogood, H.S.,Baker, H.M.,Daniel, R.M.,Baker, E.N.
Calcium-mediated thermostability in the subtilisin superfamily: the crystal structure of Bacillus Ak.1 protease at 1.8 A resolution.
J.Mol.Biol., 294:1027-1040, 1999

PubMed Abstract: Proteins of the subtilisin superfamily (subtilases) are widely distributed through many living species, where they perform a variety of processing functions. They are also used extensively in industry. In many of these enzymes, bound calcium ions play a key role in protecting against autolysis and thermal denaturation. We have determined the crystal structure of a highly thermostable protease from Bacillus sp. Ak.1 that is strongly stabilized by calcium. The crystal structure, determined at 1.8 A resolution (R=0. 182, Rfree=0.247), reveals the presence of four bound cations, three Ca(2+) and one Na(+). Two of the Ca(2+) binding sites, Ca-1 and Ca-2, correspond to sites also found in thermitase and the mesophilic subtilisins. The third calcium ion, however, is at a novel site that is created by two key amino acid substitutions near Ca-1, and has not been observed in any other subtilase. This site, acting cooperatively with Ca-1, appears to give substantially enhanced thermostability, compared with thermitase. Comparisons with the mesophilic subtilisins also point to the importance of aromatic clusters, reduced hydrophobic surface and constrained N and C termini in enhancing the thermostability of thermitase and Ak.1 protease. The Ak.1 protease also contains an unusual Cys-X-Cys disulfide bridge that modifies the active site cleft geometry.

PubMed: 10588904
DOI: 10.1006/jmbi.1999.3291

Experimental method

X-RAY DIFFRACTION (1.8 Å)