title: BtcA, A class IA type III chaperone, interacts with the BteA N-terminal domain through a globular/non-globular mechanism.
abstract: Bordetella pertussis, the etiological agent of "whooping cough" disease, utilizes the type III secretion system (T3SS) to deliver a 69 kDa cytotoxic effector protein, BteA, directly into the host cells. As with other T3SS effectors, prior to its secretion BteA binds BtcA, a 13.9 kDa protein predicted to act as a T3SS class IA chaperone. While this interaction had been characterized for such effector-chaperone pairs in other pathogens, it has yet to be fully investigated in Bordetella. Here we provide the first biochemical proof that BtcA is indeed a class IA chaperone, responsible for the binding of BteA's N-terminal domain. We bring forth extensive evidence that BtcA binds its substrate effector through a dual-interface binding mechanism comprising of non-globular and bi-globular interactions at a moderate micromolar level binding affinity. We demonstrate that the non-globular interactions involve the first 31 N-terminal residues of BteA287 and their removal leads to destabilization of the effector-chaperone complex and lower binding affinities to BtcA. These findings represent an important first step towards a molecular understanding of BteA secretion and cell entry.
authors: Departments of Life Sciences and the National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be'er Sheva, Israel.
authors: Chen
authors: C
authors: Guttman
authors: Geula
authors: G
authors: Davidov
authors: Adi
authors: A
authors: Yahalom
authors: Hadassa
authors: H
authors: Shaked
authors: Sofiya
authors: S
authors: Kolusheva
authors: Ronit
authors: R
authors: Bitton
authors: Shiran
authors: S
authors: Barber-Zucker
authors: Jordan H
authors: JH
authors: Chill
authors: Raz
authors: R
authors: Zarivach
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D001886:Bordetella pertussis / Q000378:metabolism*; D019295:Computational Biology; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012995:Solubility
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones