1EA7

Sphericase

Summary for 1EA7

• Entry DOI: 10.2210/pdb1ea7/pdb
• Descriptor: SERINE PROTEASE, CALCIUM ION (3 entities in total)
• Functional Keywords: hydrolase, serine protease, sphericase, subtilisin like protease
• Biological source: BACILLUS SPHAERICUS
• Total number of polymer chains: 1
• Total formula weight: 32145.11

Authors

Almog, O.,Gonzalez, A.,Klein, D.,Braun, S.,Shoham, G. (deposition date: 2001-07-10, release date: 2002-07-04, Last modification date: 2024-11-06)

Primary citation

Almog, O.,Gonzalez, A.,Klein, D.,Greenblat, H.M.,Braun, S.,Shoham, G.
The 0.93A Crystal Structure of Sphericase: A Calcium-Loaded Serine Protease from Bacillus Sphaericus
J.Mol.Biol., 332:1071-, 2003

PubMed Abstract: We have previously isolated sphericase (Sph), an extracellular mesophilic serine protease produced by Bacillus sphaericus. The Sph amino acid sequence is highly homologous to two cold-adapted subtilisins from Antarctic bacilli S39 and S41 (76% and 74% identity, respectively). Sph is calcium-dependent, 310 amino acid residues long and has optimal activity at pH 10.0. S41 and S39 have not as yet been structurally analysed. In the present work, we determined the crystal structure of Sph by the Eu/multiwavelength anomalous diffraction method. The structure was extended to 0.93A resolution and refined to a crystallographic R-factor of 9.7%. The final model included all 310 amino acid residues, one disulfide bond, 679 water molecules and five calcium ions. Although Sph is a mesophilic subtilisin, its amino acid sequence is similar to that of the psychrophilic subtilisins, which suggests that the crystal structure of these subtilisins is very similar. The presence of five calcium ions bound to a subtilisin molecule, as found here for Sph, has not been reported for the subtilisin superfamily. None of these calcium-binding sites correlates with the well-known high-affinity calcium-binding site (site I or site A), and only one site has been described previously. This calcium-binding pattern suggests that a reduction in the flexibility of the surface loops of Sph by calcium binding may be responsible for its adaptation to mesophilic organisms.

PubMed: 14499610
DOI: 10.1016/J.JMB.2003.07.011

Experimental method

X-RAY DIFFRACTION (0.93 Å)