Structure and membrane-targeting of a Bordetella pertussis effector N-terminal domain

Adi Yahalom; Geula Davidov; Sofiya Kolusheva; Hadassa Shaked; Shiran Barber-Zucker; Raz Zarivach; Jordan H Chill

doi:10.1016/j.bbamem.2019.183054

Structure and membrane-targeting of a Bordetella pertussis effector N-terminal domain

Biochim Biophys Acta Biomembr. 2019 Dec 1;1861(12):183054. doi: 10.1016/j.bbamem.2019.183054. Epub 2019 Sep 2.

Authors

Adi Yahalom¹, Geula Davidov², Sofiya Kolusheva², Hadassa Shaked¹, Shiran Barber-Zucker², Raz Zarivach³, Jordan H Chill⁴

Affiliations

¹ Department of Chemistry, Bar Ilan University, Ramat Gan 52900, Israel.
² Departments of Life Sciences, National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel.
³ Departments of Life Sciences, National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel. Electronic address: zarivach@bgu.ac.il.
⁴ Department of Chemistry, Bar Ilan University, Ramat Gan 52900, Israel. Electronic address: Jordan.Chill@biu.ac.il.

PMID: 31487494
DOI: 10.1016/j.bbamem.2019.183054

Abstract

BteA, a 69-kDa cytotoxic protein, is a type III secretion system (T3SS) effector in the classical Bordetella, the etiological agents of pertussis and related mammalian respiratory diseases. Like other cytotoxicity-mediating effectors, BteA uses its multifunctional N-terminal domain to target phosphatidylinositol (PI)-rich microdomains in the host membrane. Despite their structural similarity, T3SS effectors exhibit a variable range of membrane interaction modes, and currently only limited structural information is available for the BteA membrane-targeting domain and the molecular mechanisms underlying its function. Employing a synergistic combination of structural methods, here we determine the structure of this functional domain and uncover key molecular determinants mediating its interaction with membranes. Residues 29-121 of BteA form an elongated four-helix bundle packed against two shorter perpendicular helices, the second of which caps the domain in a critical 'tip motif'. A flexible region preceding the BteA helical bundle contains the characteristic β-motif required for binding its cognate chaperone BtcA. We show that BteA targets PI(4,5)P₂-containing lipoprotein nanodiscs and binds a soluble PI(4,5)P₂ analog via an extensive positively charged surface spanning its first two helices, and that this interaction is weaker for PI(3,5)P₂ and abolished for PI(4)P. We confirmed this model of membrane-targeting by observation of BteA-induced changes in the structure of PI(4,5)P₂-containing phospholipid bilayers using small-angle X-ray scattering (SAXS). We also extended these results to a larger BteA domain (residues 1-287), confirming its interaction with bilayers using calorimetry, fluorescence and SAXS methods. This novel view of the structural underpinnings of membrane targeting by BteA is an important step towards a comprehensive understanding of cytotoxicity in Bordetella, as well as interactions of a broad range of pathogens with their respective hosts.

Keywords: Bordetella; Effector; Membrane targeting; NMR spectroscopy; Type 3 secretion system; X-ray crystallography.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Sequence / genetics
Bacterial Proteins / chemistry
Bacterial Proteins / genetics
Bordetella pertussis / metabolism*
Bordetella pertussis / pathogenicity
Bordetella pertussis / ultrastructure*
Crystallography, X-Ray / methods
Cytotoxicity, Immunologic / physiology
Membrane Proteins / metabolism
Membrane Proteins / ultrastructure
Molecular Chaperones / metabolism
Phosphatidylinositols / metabolism
Protein Binding / physiology
Scattering, Small Angle
Structure-Activity Relationship
Type III Secretion Systems / metabolism*
Type III Secretion Systems / physiology
X-Ray Diffraction / methods

Substances

Bacterial Proteins
Membrane Proteins
Molecular Chaperones
Phosphatidylinositols
Type III Secretion Systems