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Structural and functional aspects of unique type IV secretory components in the Helicobacter pylori cag ‐pathogenicity island
Author(s) -
Cendron Laura,
Zanotti Giuseppe
Publication year - 2011
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2011.08038.x
Subject(s) - pathogenicity island , caga , secretion , effector , biology , pilus , peptidoglycan , helicobacter pylori , virulence , gene , structural similarity , transmembrane protein , microbiology and biotechnology , genetics , biochemistry , receptor
Helicobacter pylori cytotoxin‐associated gene ‐pathogenicity island ( cag PAI) is responsible for the secretion of the CagA effector through a type IV secretion system (T4SS) apparatus, as well as of peptidoglycan and possibly other not yet identified factors. Twenty‐nine different polypeptide chains are encoded by this cluster of genes, although only some of them show a significant similarity with the constitutive elements of well characterized secretion systems from other bacteria. The other cag PAI components represent almost unique proteins in this scenario. The majority of the T4SS include approximately fifteen components, taking into account either the transmembrane complex subunits, ATPases or substrate factors. The composition of the cag PAI is very complex: it includes proteins most likely involved at different levels in the pilus assembly, stabilization and processing of secreted substrate, as well as regulatory particles possibly involved in the control of the entire apparatus. Despite recent findings with respect to components that play a role in the interaction with the host cell, the function of several cag PAI proteins remains unclear or unknown. This is particularly true for those that represent unique members with no clear similarity to those of other T4SS and no obvious evidence of involvement in the secretion of CagA or induction of pro‐inflammatory responses. We summarize what is known about these accessory components, both from a molecular and structural point of view, as well as their putative physiological role.