View source for 31vh


==Alcalase/CI-2A complex at 277K==
<StructureSection load='31vh' size='340' side='right'caption='[[31vh]], [[Resolution|resolution]] 1.05&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[31vh]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Bacillus_licheniformis Bacillus licheniformis] and [https://en.wikipedia.org/wiki/Hordeum_vulgare Hordeum vulgare]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=31VH OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=31VH FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.05&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=31vh FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=31vh OCA], [https://pdbe.org/31vh PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=31vh RCSB], [https://www.ebi.ac.uk/pdbsum/31vh PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=31vh ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/Q9FDF2_BACLI Q9FDF2_BACLI] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Serine proteases catalyze peptide-bond hydrolysis through a conserved catalytic triad and an extensive network of hydrogen bonds that facilitate proton transfer and stabilization of reaction intermediates. Despite decades of study, the nature of the hydrogen-bonding interactions within the catalytic machinery remains incompletely understood. Here, we report ultra-high-resolution crystal structures of alcalase, a subtilisin-family serine protease, in complex with native chymotrypsin inhibitor 2A (CI-2 A) and with a low-affinity M59P inhibitor variant. The cryogenic structures were determined at 0.74 A resolution, while an additional 4 degrees C (277 K) structure of the native complex was determined at 1.05 A resolution. The data allowed visualization and refinement of numerous hydrogen atoms within the active site and at the enzyme-inhibitor interface. Comparison of the 4 degrees C and cryogenic structures revealed a systematic shortening of hydrogen-bond donor-acceptor distances upon cooling, consistent with the global lattice contraction. A notable exception was the hydrogen bond between the catalytic residues Ser221 and His64, which remained unusually short at both temperatures. In the 4 degrees C structure, the corresponding hydrogen atom is associated with weak and diffuse electron density, suggesting increased proton mobility within this interaction. The structures further reveal temperature-dependent differences in interactions involving the scissile peptide bond of the inhibitor and the conserved backbone carbonyl oxygen of Ser125. These observations support a model in which Ser125 participates in a concerted hydrogen-bond network coupled to proton transfer within the catalytic triad. Together, the results provide atomic-level insights into hydrogen bonding, protonation equilibria, and catalytic mechanism in subtilisin-like serine proteases.

Catalytic hydrogen bonds in alcalase-CI-2A complexes revealed by ultra-high-resolution crystallography.,Raczynska JE, Jedrzejczak R, Dauter M, Ostergaard PR, Wilson KS, Rypniewski W J Struct Biol. 2026 Sep 25;218(4):108377. doi: 10.1016/j.jsb.2026.108377. PMID:42790760<ref>PMID:42790760</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 31vh" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Bacillus licheniformis]]
[[Category: Hordeum vulgare]]
[[Category: Large Structures]]
[[Category: Rypniewski W]]