View source for 9vqn


==Crystal structure of Se-Met SSA1633 from Streptococcus sanguinis (Phase determination model)==
<StructureSection load='9vqn' size='340' side='right'caption='[[9vqn]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9vqn]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Streptococcus_sanguinis Streptococcus sanguinis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9VQN OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9VQN 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]] 2.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MSE:SELENOMETHIONINE'>MSE</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=9vqn FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9vqn OCA], [https://pdbe.org/9vqn PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9vqn RCSB], [https://www.ebi.ac.uk/pdbsum/9vqn PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9vqn ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A3CPB6_STRSV A3CPB6_STRSV] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Bacterial pili are proteinaceous polymers that facilitate diverse biological functions. The SK36 strain of oral commensal bacterium Streptococcus sanguinis harbors sortase-assembled pili consisting of four proteins; PilA, PilB, PilC, and PilX. However, details regarding their structures and assembly mechanisms remain unclear. The crystal structures of recombinant PilA and PilB backbone pilins were examined at resolutions of 3.2 A and 1.8 A, respectively. Both exhibit a three-domain architecture (domains 1-3 from N- to C- terminus) with intramolecular isopeptide bonds in domains 2 and 3, and a positively charged, highly hydrophobic cleft in domain 1. Notably, while alignment along the same axis within the crystal was noted, their molecular orientations differ, as PilA maintains identical orientations (linear form), whereas PilB molecules are flipped 180 degrees relative to each other (helical form). Both recognize the conserved ALLPNT sequence of domain 3 via the domain 1 cleft. Fragment molecular orbital calculations revealed no significant energetic differences between the linear and helical forms, with interactions predominantly mediated by C-terminal asparagine and threonine residues. Immunoblot analysis confirmed intermolecular isopeptide bond formation between threonine and conserved lysine residues at the domain 1-2 interface. The preceding glycine residue in the GALLPNT sequence may serve as a flexible pivot, enabling transitions between both forms. Since PilA, PilB, and PilC contain the GALLPNT sequence and could interconnect, the observations of domain 1-mediated recognition of the domain 3 C-terminal region indicate a fundamental mechanism governing S. sanguinis pilus assembly. These findings provide molecular-based insight into sortase-mediated pilus biogenesis in Gram-positive bacteria.

Combined structural and FMO-based insights into shaft pilin polymerization mechanism in Streptococcus sanguinis.,Takebe K, Miyakawa S, Sangawa T, Suzuki M, Matsumoto A, Oogai Y, Yamaguchi M, Sumitomo T, Fukuzawa K, Kawabata S, Nakata M Int J Biol Macromol. 2025 Dec;332(Pt 2):148264. doi: , 10.1016/j.ijbiomac.2025.148264. Epub 2025 Oct 12. PMID:41086886<ref>PMID:41086886</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 9vqn" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Streptococcus sanguinis]]
[[Category: Nakata M]]
[[Category: Suzuki M]]
[[Category: Takebe K]]