Structural and mechanistic analysis of a tripartite ATP-independent periplasmic TRAP transporter

• DOI: 10.1038/s41467-022-31907-y
• Publication Date: 2022-08-04T10:03:24Z
• Authors: Martin F. Peter; Jan A. Ruland; Peer Depping; Niels Schneberger; Emmanuele Severi; Jonas Moecking; Karl Gatterdam; Sarah Tindall; Alexandre Durand; Veronika Heinz; Jan Peter Siebrasse; Paul-Albert Koenig; Matthias Geyer; Christine Ziegler; Ulrich Kubitscheck; Gavin H. Thomas; Gregor Hagelueken
• Keywords: Trap (plumbing); Structural Biology

Tripartite ATP-independent periplasmic (TRAP) transporters are found widely in bacteria and archaea consist of three structural domains, a soluble substrate-binding protein (P-domain), two transmembrane domains (Q- M-domains). HiSiaPQM its homologs TRAP for sialic acid essential host colonization by pathogenic bacteria. Here, we reconstitute HiSiaQM into lipid nanodiscs use cryo-EM to reveal the structure transporter. It is composed 16 helices that unexpectedly structurally related multimeric elevator-type transporters. The idiosyncratic Q-domain enables formation monomeric elevator architecture. A model tripartite PQM complex experimentally validated reveals coupling transporter domains. We single-molecule total internal reflection fluorescence (TIRF) microscopy solid-supported bilayers surface plasmon resonance study investigate impact interface mutants. Furthermore, characterize high-affinity single variable on heavy chain (VHH) antibodies bind side inhibit uptake, providing insight how function might be inhibited vivo.