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The structure of nontypeable Haemophilus influenzae SapA in a closed conformation reveals a constricted ligand-binding cavity and a novel RNA binding motif
DOI:
10.1371/journal.pone.0256070
Authors:
Petra
Lukacik
(Diamond Light Source)
,
C. David
Owen
(Diamond Light Source)
,
Gemma
Harris
(Research Complex at Harwell)
,
Jani Reddy
Bolla
(University of Oxford)
,
Sarah
Picaud
(Structural Genomics Consortium, University of Oxford)
,
Irfan
Alibay
(University of Oxford)
,
Joanne E.
Nettleship
(Research Complex at Harwell; Wellcome Trust Centre for Human Genetics, University of Oxford)
,
Louise E.
Bird
(Research Complex at Harwell; Wellcome Trust Centre for Human Genetics, University of Oxford)
,
Raymond
Owens
(Research Complex at Harwell; Wellcome Trust Centre for Human Genetics, University of Oxford)
,
Philip C.
Biggin
(University of Oxford)
,
Panagis
Filippakopoulos
(Structural Genomics Consortium, University of Oxford)
,
Carol V.
Robinson
(University of Oxford)
,
Martin A.
Walsh
(Diamond Light Source)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Plos One
, VOL 16
State:
Published (Approved)
Published:
October 2021
Diamond Proposal Number(s):
4990
,
5073
,
4988

Abstract: Nontypeable Haemophilus influenzae (NTHi) is a significant pathogen in respiratory disease and otitis media. Important for NTHi survival, colonization and persistence in vivo is the Sap (sensitivity to antimicrobial peptides) ABC transporter system. Current models propose a direct role for Sap in heme and antimicrobial peptide (AMP) transport. Here, the crystal structure of SapA, the periplasmic component of Sap, in a closed, ligand bound conformation, is presented. Phylogenetic and cavity volume analysis predicts that the small, hydrophobic SapA central ligand binding cavity is most likely occupied by a hydrophobic di- or tri- peptide. The cavity is of insufficient volume to accommodate heme or folded AMPs. Crystal structures of SapA have identified surface interactions with heme and dsRNA. Heme binds SapA weakly (Kd 282 μM) through a surface exposed histidine, while the dsRNA is coordinated via residues which constitute part of a conserved motif (estimated Kd 4.4 μM). The RNA affinity falls within the range observed for characterized RNA/protein complexes. Overall, we describe in molecular-detail the interactions of SapA with heme and dsRNA and propose a role for SapA in the transport of di- or tri-peptides.
Journal Keywords: Heme; Crystal structure; Crystals; Escherichia coli; RNA structure; Ribosomal RNA; Crystallization; Protein domains
Diamond Keywords: Bacteria
Subject Areas:
Biology and Bio-materials
Instruments:
I04-1-Macromolecular Crystallography (fixed wavelength)
,
I04-Macromolecular Crystallography
Added On:
18/10/2021 11:31
Documents:
journal.pone.0256070.pdf
Discipline Tags:
Pathogens
Antibiotic Resistance
Infectious Diseases
Health & Wellbeing
Structural biology
Life Sciences & Biotech
Technical Tags:
Diffraction
Macromolecular Crystallography (MX)