New insights about pilus formation in gut-adapted Lactobacillus rhamnosus GG from the crystal structure of the SpaA backbone-pilin subunit

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http://hdl.handle.net/10138/165172

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Chaurasia , P , Pratap , S , von Ossowski , I , Palva , A & Krishnan , V 2016 , ' New insights about pilus formation in gut-adapted Lactobacillus rhamnosus GG from the crystal structure of the SpaA backbone-pilin subunit ' , Scientific Reports , vol. 6 , 28664 . https://doi.org/10.1038/srep28664

Title: New insights about pilus formation in gut-adapted Lactobacillus rhamnosus GG from the crystal structure of the SpaA backbone-pilin subunit
Author: Chaurasia, Priyanka; Pratap, Shivendra; von Ossowski, Ingemar; Palva, Airi; Krishnan, Vengadesan
Contributor: University of Helsinki, Departments of Faculty of Veterinary Medicine
University of Helsinki, Departments of Faculty of Veterinary Medicine
Date: 2016-06-28
Language: eng
Number of pages: 17
Belongs to series: Scientific Reports
ISSN: 2045-2322
URI: http://hdl.handle.net/10138/165172
Abstract: Thus far, all solved structures of pilin-proteins comprising sortase-assembled pili are from pathogenic genera and species. Here, we present the first crystal structure of a pilin subunit (SpaA) from a nonpathogen host (Lactobacillus rhamnosus GG). SpaA consists of two tandem CnaB-type domains, each with an isopeptide bond and E-box motif. Intriguingly, while the isopeptide bond in the N-terminal domain forms between lysine and asparagine, the one in the C-terminal domain atypically involves aspartate. We also solved crystal structures of mutant proteins where residues implicated in forming isopeptide bonds were replaced. Expectedly, the E-box-substituted E139A mutant lacks an isopeptide bond in the N-terminal domain. However, the C-terminal E269A substitution gave two structures; one of both domains with their isopeptide bonds present, and another of only the N-terminal domain, but with an unformed isopeptide bond and significant conformational changes. This latter crystal structure has never been observed for any other Gram-positive pilin. Notably, the C-terminal isopeptide bond still forms in D295N-substituted SpaA, irrespective of E269 being present or absent. Although E-box mutations affect SpaA proteolytic and thermal stability, a cumulative effect perturbing normal pilus polymerization was unobserved. A model showing the polymerized arrangement of SpaA within the SpaCBA pilus is proposed.
Subject: GRAM-POSITIVE BACTERIA
INTRAMOLECULAR ISOPEPTIDE BONDS
STREPTOCOCCUS-PNEUMONIAE
CORYNEBACTERIUM-DIPHTHERIAE
CRYSTALLOGRAPHIC ANALYSIS
STABILIZING ISOPEPTIDE
FUNCTIONAL-ANALYSIS
SPACBA PILUS
CROSS-LINKS
PROTEIN
1182 Biochemistry, cell and molecular biology
3111 Biomedicine
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