1st3
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(New page: 200px<br /><applet load="1st3" size="450" color="white" frame="true" align="right" spinBox="true" caption="1st3, resolution 1.4Å" /> '''THE CRYSTAL STRUCTURE...)
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THE CRYSTAL STRUCTURE OF THE BACILLUS LENTUS ALKALINE PROTEASE, SUBTILISIN BL, AT 1.4 ANGSTROMS RESOLUTION
Overview
The crystal structure of subtilisin BL, an alkaline protease from Bacillus, lentus with activity at pH 11, has been determined to 1.4 A resolution., The structure was solved by molecular replacement starting with the 2.1 A, structure of subtilisin BPN' followed by molecular dynamics refinement, using X-PLOR. A final crystallographic R-factor of 19% overall was, obtained. The enzyme possesses stability at high pH, which is a result of, the high pI of the protein. Almost all of the acidic side-chains are, involved in some type of electrostatic interaction (ion pairs, calcium, binding, etc.). Furthermore, three of seven tyrosine residues have, potential partners for forming salt bridges. All of the potential partners, are arginine with a pK around 12. Lysine would not function well in a salt, bridge with tyrosine as it deprotonates at around the same pH as tyrosine, ionizes. Stability at high pH is acquired in part from the pI of the, protein, but also from the formation of salt bridges (which would affect, the pI). The overall structure of the enzyme is very similar to other, subtilisins and shows that the subtilisin fold is more highly conserved, than would be expected from the differences in amino acid sequence. The, amino acid side-chains in the hydrophobic core are not conserved, though, the inter-residue interactions are. Finally, one third of the serine, side-chains in the protein have multiple conformations. This presents an, opportunity to correlate computer simulations with observed occupancies in, the crystal structure.
About this Structure
1ST3 is a Single protein structure of sequence from Bacillus lentus with CA as ligand. Active as Subtilisin, with EC number 3.4.21.62 Full crystallographic information is available from OCA.
Reference
The crystal structure of the Bacillus lentus alkaline protease, subtilisin BL, at 1.4 A resolution., Goddette DW, Paech C, Yang SS, Mielenz JR, Bystroff C, Wilke ME, Fletterick RJ, J Mol Biol. 1992 Nov 20;228(2):580-95. PMID:1453465
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