title: Biochemical Analysis of CagE: A VirB4 Homologue of Helicobacter pylori Cag-T4SS.
abstract: Helicobacter pylori are among the most successful human pathogens that harbour a distinct genomic segment called cag Pathogenicity Island (cag-PAI). This genomic segment codes for a type IV secretion system (Cag-T4SS) related to the prototypical VirB/D4 system of Agrobacterium tumefaciens (Ag), a plant pathogen. Some of the components of Cag-T4SS share homology to that of VirB proteins including putative energy providing CagE (HP0544), the largest VirB4 homologue. In Ag, VirB4 is required for the assembly of the system, substrate translocation and pilus formation, however, very little is known about CagE. Here we have characterised the protein biochemically, genetically, and microscopically and report that CagE is an inner membrane associated active NTPase and has multiple interacting partners including the inner membrane proteins CagV and Cagβ. Through CagV it is connected to the outer membrane sub-complex proteins. Stability of CagE is not dependent on several of the cag-PAI proteins tested. However, localisation and stability of the pilus associated CagI, CagL and surface associated CagH are affected in its absence. Stability of the inner membrane associated energetic component Cagβ, a VirD4 homologue seems to be partially affected in its absence. Additionally, CagA failed to cross the membrane barriers in its absence and no IL-8 induction is observed under infection condition. These results thus suggest the importance of CagE in Cag-T4SS functions. In future it may help in deciphering the mechanism of substrate translocation by the system.
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.|School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Mohd
authors.initials: M
authors.lastname: Shariq
authors.affiliation: Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Navin
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumari
authors.affiliation: School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Amarjeet
authors.initials: A
authors.lastname: Kumar
authors.affiliation: School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Naidu
authors.initials: N
authors.lastname: Subbarao
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Gauranga
authors.initials: G
authors.lastname: Mukhopadhyay
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis / Q000378:metabolism; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D016481:Helicobacter Infections / Q000378:metabolism / Q000382:microbiology*; D016480:Helicobacter pylori / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D043583:Nucleoside-Triphosphatase / Q000032:analysis / Q000378:metabolism*; D011487:Protein Conformation; D060066:Protein Interaction Maps; D055550:Protein Stability
chemical_list: D001426:Bacterial Proteins; C103937:PicB protein, Helicobacter pylori; D000251:Adenosine Triphosphatases; D043583:Nucleoside-Triphosphatase