6PY3

Crystal structure of ligand-binding domain of Pseudomonas fluorescens chemoreceptor CtaA in complex with L-isoleucine

Summary for 6PY3

• Entry DOI: 10.2210/pdb6py3/pdb
• Descriptor: Putative methyl-accepting chemotaxis protein, ISOLEUCINE (3 entities in total)
• Functional Keywords: bacterial chemotaxis, chemoreceptor, double cache, ligand binding domain, signaling protein
• Biological source: Pseudomonas fluorescens (strain Pf0-1)
• Total number of polymer chains: 2
• Total formula weight: 54373.34

Authors

Ud-Din, I.A.,Khan, M.F.,Roujeinikova, A. (deposition date: 2019-07-28, release date: 2020-03-18, Last modification date: 2023-10-11)

Primary citation

Ud-Din, A.I.M.S.,Khan, M.F.,Roujeinikova, A.
Broad Specificity of Amino Acid Chemoreceptor CtaA ofPseudomonas fluorescensIs Afforded by Plasticity of Its Amphipathic Ligand-Binding Pocket.
Mol.Plant Microbe Interact., 33:612-623, 2020

PubMed Abstract: Motile bacteria follow gradients of nutrients or other environmental cues. Many bacterial chemoreceptors that sense exogenous amino acids contain a double Cache (dCache; calcium channels and chemotaxis receptors) ligand-binding domain (LBD). A growing number of studies suggest that broad-specificity dCache-type receptors that sense more than one amino acid are common. Here, we present an investigation into the mechanism by which the dCache LBD of the chemoreceptor CtaA from a plant growth-promoting rhizobacterium, , recognizes several chemically distinct amino acids. We established that amino acids that signal by directly binding to the CtaA LBD include ones with aliphatic (l-alanine, l-proline, l-leucine, l-isoleucine, l-valine), small polar (l-serine), and large charged (larginine) side chains. We determined the structure of CtaA LBD in complex with different amino acids, revealing that its ability to recognize a range of structurally and chemically distinct amino acids is afforded by its easily accessible plastic pocket, which can expand or contract according to the size of the ligand side chain. The amphipathic character of the pocket enables promiscuous interactions with both polar and nonpolar amino acids. The results not only clarify the means by which various amino acids are recognized by CtaA but also reveal that a conserved mobile lid over the ligand-binding pocket adopts the same conformation in all complexes, consistent with this being an important and invariant part of the signaling mechanism.

PubMed: 31909676
DOI: 10.1094/MPMI-10-19-0277-R

Experimental method

X-RAY DIFFRACTION (1.9 Å)