PDBsum entry 4z9c

Transferase

PDB id: 4z9c

Contents

Protein chains

223 a.a.

115 a.a.

Ligands

PO4

Waters ×64

References listed in PDB file

Key reference

• Title: Structure-Function analyses of a pertussis-Like toxin from pathogenicescherichia colireveal a distinct mechanism of inhibition of trimeric g-Proteins.
• Authors: D.R.Littler, S.Y.Ang, D.G.Moriel, M.Kocan, O.Kleifeld, M.D.Johnson, M.T.Tran, A.W.Paton, J.C.Paton, R.J.Summers, M.A.Schembri, J.Rossjohn, T.Beddoe.
• Ref.: J Biol Chem, 2017, 292, 15143-15158.
• PubMed id: 28663369

Abstract

Pertussis-like toxins are secreted by several bacterial pathogens during infection. They belong to the AB₅virulence factors, which bind to glycans on host cell membranes for internalization. Host cell recognition and internalization are mediated by toxin B subunits sharing a unique pentameric ring-like assembly. Although the role of pertussis toxin in whooping cough is well-established, pertussis-like toxins produced by other bacteria are less studied, and their mechanisms of action are unclear. Here, we report that some extra-intestinalEscherichia colipathogens (i.e.those that reside in the gut but can spread to other bodily locations) encode a pertussis-like toxin that inhibits mammalian cell growthin vitroWe found that this protein,EcPlt, is related to toxins produced by both nontyphoidal and typhoidalSalmonellaserovars. Pertussis-like toxins are secreted as disulfide-bonded heterohexamers in which the catalytic ADP-ribosyltransferase subunit is activated when exposed to the reducing environment in mammalian cells. We found here that the reducedEcPlt exhibits large structural rearrangements associated with its activation. We noted that inhibitory residues tethered within the NAD⁺-binding site by an intramolecular disulfide in the oxidized state dissociate upon the reduction and enable loop restructuring to form the nucleotide-binding site. Surprisingly, although pertussis toxin targets a cysteine residue within the α subunit of inhibitory trimeric G-proteins, we observed that activatedEcPlt toxin modifies a proximal lysine/asparagine residue instead. In conclusion, our results reveal the molecular mechanism underpinning activation of pertussis-like toxins, and we also identified differences in host target specificity.