8THJ

Cryo-EM structure of the Tripartite ATP-independent Periplasmic (TRAP) transporter SiaQM from Haemophilus influenzae (antiparallel dimer)

Summary for 8THJ

• Entry DOI: 10.2210/pdb8thj/pdb
• EMDB information: 41265 41266
• Descriptor: Sialic acid TRAP transporter permease protein SiaT, SODIUM ION, PHOSPHATIDYLETHANOLAMINE, ... (4 entities in total)
• Functional Keywords: sugar transport, sialic acid, trap transporter, secondary active transport, ion transporter superfamily, transport protein
• Biological source: Haemophilus influenzae Rd KW20
• Total number of polymer chains: 2
• Total formula weight: 147155.71

Authors

Davies, J.S.,Currie, M.C.,Dobson, R.C.J.,North, R.A. (deposition date: 2023-07-16, release date: 2023-11-22, Last modification date: 2024-02-28)

Primary citation

Currie, M.J.,Davies, J.S.,Scalise, M.,Gulati, A.,Wright, J.D.,Newton-Vesty, M.C.,Abeysekera, G.S.,Subramanian, R.,Wahlgren, W.Y.,Friemann, R.,Allison, J.R.,Mace, P.D.,Griffin, M.D.W.,Demeler, B.,Wakatsuki, S.,Drew, D.,Indiveri, C.,Dobson, R.C.J.,North, R.A.
Structural and biophysical analysis of a Haemophilus influenzae tripartite ATP-independent periplasmic (TRAP) transporter.
Elife, 12:-, 2024

PubMed Abstract: Tripartite ATP-independent periplasmic (TRAP) transporters are secondary-active transporters that receive their substrates via a soluble-binding protein to move bioorganic acids across bacterial or archaeal cell membranes. Recent cryo-electron microscopy (cryo-EM) structures of TRAP transporters provide a broad framework to understand how they work, but the mechanistic details of transport are not yet defined. Here we report the cryo-EM structure of the -acetylneuraminate TRAP transporter (SiaQM) at 2.99 Å resolution (extending to 2.2 Å at the core), revealing new features. The improved resolution (the previous SiaQM structure is 4.7 Å resolution) permits accurate assignment of two Na sites and the architecture of the substrate-binding site, consistent with mutagenic and functional data. Moreover, rather than a monomer, the SiaQM structure is a homodimer. We observe lipids at the dimer interface, as well as a lipid trapped within the fusion that links the SiaQ and SiaM subunits. We show that the affinity () for the complex between the soluble SiaP protein and SiaQM is in the micromolar range and that a related SiaP can bind SiaQM. This work provides key data that enhances our understanding of the 'elevator-with-an-operator' mechanism of TRAP transporters.

PubMed: 38349818
DOI: 10.7554/eLife.92307

Experimental method

ELECTRON MICROSCOPY (2.99 Å)