6AA1

Crystal structure of putative amino acid binding periplasmic ABC transporter protein from Candidatus Liberibacter asiaticus bound with citrate

Summary for 6AA1

• Entry DOI: 10.2210/pdb6aa1/pdb
• Descriptor: Putative amino acid-binding periplasmic ABC transporter protein, GLYCEROL, 1,2-ETHANEDIOL, ... (6 entities in total)
• Functional Keywords: candidatus liberibacter asiaticus, periplasmic, abc transporter, solute binding, citrate, transport protein
• Biological source: Liberibacter asiaticus (strain psy62)
• Total number of polymer chains: 2
• Total formula weight: 58600.65

Authors

Kumar, P.,Kesari, P.,Ghosh, D.K.,Kumar, P.,Sharma, A.K. (deposition date: 2018-07-16, release date: 2019-06-12, Last modification date: 2024-10-16)

Primary citation

Kumar, P.,Kesari, P.,Kokane, S.,Ghosh, D.K.,Kumar, P.,Sharma, A.K.
Crystal structures of a putative periplasmic cystine-binding protein from Candidatus Liberibacter asiaticus: insights into an adapted mechanism of ligand binding.
Febs J., 286:3450-3472, 2019

PubMed Abstract: The amino acid-binding receptors, a component of ABC transporters, have evolved to cater to different specificities and functions. Of particular interest are cystine-binding receptors, which have shown broad specificity. In the present study, a putative periplasmic cystine-binding protein from Candidatus Liberibacter asiaticus (CLasTcyA) was characterized. Analysis of the CLasTcyA sequence and crystal structures in the ligand-bound state revealed novel features of CLasTcyA in comparison to related proteins. One of the unique features found in CLasTcyA structure was the positioning of the C-terminal extended loop of one chain very close to the substrate-binding site of the adjacent monomer in the asymmetric unit. The presence of a disulphide bond, unique to Candidatus Liberibacter family, holds the C-terminal extended loop in position. Analysis of the substrate-binding pocket of CLasTcyA suggested a broad specificity and a completely different orientation of the bound substrates in comparison to related protein structures. The open conformation for one of the two chains of the asymmetric unit in the Arg-bound structure revealed a limited open state (18.4°) for CLasTcyA as compared to open state of other related proteins (~ 60°). The strong interaction between Asp126 on helix-α5 of small domain and Arg82 (bigger domain) restricts the degree of opening in ligand-free open state. The dissociation constant of 1.26 μm by SPR and 3.7 μm by MST exhibited low affinity for the cystine. This is the first structural characterization of an l-cystine ABC transporter from plant pathogen and our results suggest that CLasTcyA may have evolved to cater to its specific needs for its survival in the host.

PubMed: 31063259
DOI: 10.1111/febs.14921

Experimental method

X-RAY DIFFRACTION (1.86 Å)