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E u r o S c i C o n c o n f e r e n c e o n
Protein, Proteomics and
Computational Biology
Biochemistry & Molecular Biology Journal
ISSN: 2471-8084
D e c e m b e r 0 6 - 0 7 , 2 0 1 8
Am s t e r d a m , N e t h e r l a n d s
Proteomics and Computational Biology 2018
Page 23
Y
ersinia
enterocolitica
is an opportunistic pathogen which causes enteric diseases like gastroenteritis and mesenteric adenitis
in immune-compromised individuals. The gastrointestinal phase of
Y. enterocolitica
infection is mediated by
Yersinia
secretion
apparatus -
Yersinia
secretion protein (Ysa-Ysp) Type III Secretion System (T3SS). Enhanced virulence of
Y. enterocolitica
Biovar
1B is attributed to the activation of Ysa-Ysp T3SS, which is further regulated by the formation of functional injectisome. YspB and
YspC are hydrophobic translocator proteins which are responsible for the formation of functional translocon at the tip of the needle
complex. These translocators are sequestered in the bacterial cytoplasm by their cognate chaperone SycB. SycB plays the dual role
of a class II chaperone and a regulator of Ysa-Ysp T3SS. Homology model of SycB depicts a structure with a concave core formed by
tetratricopeptide repeats (TPRs) and a flexible N-terminal helix. Deletion mutants of SycB showed that the N-terminal helix of SycB is
responsible for its dimerization, which is further corroborated by molecular docking analysis. The dimeric state of SycB dissociates
during the interactionwithYspCdue to steric hindrance. It forms a 1:1 heterodimericYspC-SycBcomplex as confirmedby size-exclusion
chromatography, chemical cross-linking and molecular docking studies. FRET analysis indicated that the tyrosine residues present in
first two TPRs of SycB is responsible for its interaction with YspC. Deletion mutants of SycB possessing the first two TPR regions
interacted with YspC, as depicted by the YspC-SycB interaction model. YspC is a unique minor translocator protein having monomeric
form with high stability and rigid tertiary structure unlike any other translocator proteins. It shows structural alteration in the complex
form with SycB as shown by spectroscopic data and proteolytic digestion. YspC has a Y-shaped three dimensional structure and SycB
completely localizes within the fork formed by the two arms of Y-shaped YspC. Like other major translocator proteins YspB possesses
a highly helical structure and transmembrane helices required for its translocation through the narrow conduit of the needle and its
insertion within the host cell plasma membrane. Being a translocator protein it has to interact with chaperones and other translocators,
which is evident from the existence of intramolecular coiled-coil regions in YspB structure. The YspB model depicted a star-shaped
structure with alpha helices interspersed by random coil regions. The inner concave core of SycB forms the interface of interaction
with YspB. This interaction is polar or ionic in nature and mediated by the first two TPRs of SycB. Therefore, simultaneous binding of
YspB and YspC to SycB is not possible due to the common interaction domains. ConSurf analysis predicted that the evolutionarily
conserved residues are mostly present in the regions of YspB involved in interaction with SycB. Exposure of translocator proteins to
the extra-cellular milieu makes them potential drug targets. Therefore, elucidation of the three dimensional structure of translocators
would enable us to determine precise antigenic epitopes for drug targeting. Structural analysis and understanding the mechanism of
interaction between translocators and chaperones would be beneficial in designing peptide drugs to deregulate the Ysa-Ysp T3SS and
attenuate the virulence of
Yersinia enterocolitica
.
Deciphering the Structural Basis of
Translocator-Chaperone Interaction of Type
III Secretion System-A Key to Drug Design
Against Pathogenic
Yersinia enterocolitica
Abhishek Basu
1
, Debjani Mandal
1
, Manali
Biswas
1
, Indranil Saha
2
and Shamsuzzaman Ahmed
2
1
Department of Molecular Biology and Biotechnology, Sripat Singh College, University of Kalyani, India
2
Department of Chemistry, Sripat Singh College, University of Kalyani, India
Abhishek Basu et al., Biochem Mol biol J Volume:4
DOI: 10.21767/2471-8084-C5-020