PDBsum entry 6a8s

Transport protein

PDB id: 6a8s

Contents

Protein chains

234 a.a.

Ligands

SO4 ×3

EDO ×22

TRS

ACT ×3

GOL ×2

CYS ×2

Waters ×175

PDB id:

6a8s

Name:

Transport protein

Title:

Crystal structure of the putative amino acid-binding periplasmic abc transporter protein from candidatus liberibacter asiaticus in complex with cysteine

Structure:

Putative amino acid-binding periplasmic abc transporter protein. Chain: a, b. Engineered: yes

Source:

Liberibacter asiaticus (strain psy62). Organism_taxid: 537021. Strain: psy62. Gene: clibasia_05070. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.05Å R-factor: 0.200 R-free: 0.258

Authors:

P.Kumar,P.Kesari,D.K.Ghosh,P.Kumar,A.K.Sharma

Key ref:

P.Kumar et al. (2019). 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. PubMed id: 31063259 DOI: 10.1111/febs.14921

Date:

10-Jul-18 Release date: 12-Jun-19

Protein chains

C6XGT2  (C6XGT2_LIBAP) -  Putative amino acid-binding periplasmic ABC transporter protein from Liberibacter asiaticus (strain psy62)

Seq: 274 a.a.

Struc: 234 a.a.

DOI no: 10.1111/febs.14921

FEBS J 286:3450-3472 (2019)

PubMed id: 31063259

Crystal structures of a putative periplasmic cystine-binding protein from Candidatus Liberibacter asiaticus: insights into an adapted mechanism of ligand binding.

P.Kumar, P.Kesari, S.Kokane, D.K.Ghosh, P.Kumar, A.K.Sharma.

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.