Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

A chemoreceptor in Campylobacter jejuni responds to multiple classes of chemoeffectors (#313)

Bassam A Elgamoudi 1 , Ekaterina P Andrianova 2 , Christopher J Day 1 , Rebecca M King 1 , Hossinur Rahman 1 , Lauren E Hartley-Tassell 1 , Igor B Zhulin 2 , Victoria Korolik 1
  1. Institute for Glycomics, Southport, QLD, Australia
  2. Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA

Tlp10 is a chemoreceptor in C. jejuni, which has a classical transmembrane topology, but its periplasmic ligand-binding domain (LBD) does not match any known domain model and its ligands were unknown. Here, we show that Tlp10 LBD has a bimodular architecture and its predicted secondary structure is reminiscent of the HBM (helical bimodular) domain found primarily in Pseudomonas; however, we found no evidence for its homology to HBM or any other helical domain (e.g. four-helix bundle). Using glycan arrays and surface plasmon resonance, we found that Tlp10 LBD binds fucose, galactose, mannose, lactose and Neu5Acα2 (sialic acid), all of which are known to play a role in initial colonisation of the host by the C. jejuni. The disassociation equilibrium constant (KD) of Tlp10 LBD for these glycans ranged between 2.9 μM and 39 μM.  Modified nutrient depleted chemotaxis assay was used to reveal that Tlp10 was also able to respond to isoleucine, purine, malic acid, α-ketoglutarate, aspartate and fumaric acid, as attractants, and to arginine and thiamine, as repellents. We identified several highly conserved amino acid residues in Tlp10 LBD (e.g. Y70, D71, F111, K112, N115, N120, S121, and H193) that suggest more than one chemoeffector binding site, which is consistent with the observed multiple chemoreceptor specificity of the Tlp10 chemoreceptor. The evolutionary genomics analysis indicates that Tlp10 LBD was born as a sensory domain in Pseudomonas histidine kinases and then propagated to other signal transduction proteins, such as c-di-GMP turnover enzymes and chemoreceptors, and to other phylogenetic groups, such as epsilon-proteobacteria, including Campylobacter and Helicobacter, as well as cyanobacteria via domain shuffling events and horizontal gene transfer. Tlp10 LBD might be the first example of a sensory domain with specificity to glycans, amino acids, organic acids, and nucleotides.