Download MendeleyStructural and biophysical analysis of a Haemophilus influenzae tripartite ATP-independent periplasmic (TRAP) transporter.
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.(2024) Elife 12
- PubMed: 38349818
- DOI: https://doi.org/10.7554/eLife.92307
- Primary Citation of Related Structures:
8THI, 8THJ - 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 Haemophilus influenzae N -acetylneuraminate TRAP transporter ( Hi SiaQM) at 2.99 Å resolution (extending to 2.2 Å at the core), revealing new features. The improved resolution (the previous Hi 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 Hi 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 ( K D ) for the complex between the soluble Hi SiaP protein and Hi SiaQM is in the micromolar range and that a related SiaP can bind Hi SiaQM. This work provides key data that enhances our understanding of the 'elevator-with-an-operator' mechanism of TRAP transporters.
Organizational Affiliation:
Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
