The Pneumococcal Iron Uptake Protein A (PiuA) Specifically Recognizes Tetradentate FeIIIbis- and Mono-Catechol Complexes

Abstract

Streptococcus pneumoniae (Spn) is an important Gram-positive human pathogen that causes millions of infections worldwide with an increasing occurrence of antibiotic resistance. Fe acquisition is a crucial virulence determinant in Spn; further, Spn relies on exogenous Fe III -siderophore scavenging to meet nutritional Fe needs. Recent studies suggest that the human catecholamine stress hormone, norepinephrine (NE), facilitates Fe acquisition in Spn under conditions of transferrin-mediated Fe starvation. Here we show that the solute binding lipoprotein PiuA from the piu Fe acquisition ABC transporter PiuBCDA, previously described as an Fe-hemin binding protein, binds tetradentate catechol Fe III complexes, including NE and the hydrolysis products of enterobactin. Two protein-derived ligands (H238, Y300) create a coordinately-saturated Fe III complex, which parallel recent studies in the Gram-negative intestinal pathogen Campylobacter jejuni. Our in vitro studies using NMR spectroscopy and 54 Fe LC-ICP-MS confirm the Fe III can move from transferrin to apo-PiuA in a NE-dependent manner. Structural analysis of PiuA Fe III -bis-catechol and Ga III -bis-catechol and Ga III -(NE)2 complexes by NMR spectroscopy reveals only localized structural perturbations in PiuA upon ligand binding, largely consistent with recent descriptions of other solute binding proteins of type II ABC transporters. We speculate that tetradentate Fe III complexes formed by mono-and bis-catechol species are important Fe sources in Gram-positive human pathogens, since PiuA functions in the same way as SstD from Staphylococcus aureus.

Opportunistic use of catecholamine neurotransmitters as siderophores to access iron by Pseudomonas aeruginosa

“…PiuA in P . aeruginosa is a TBDT and not a solute binding lipoprotein associated to the ABC transporter PiuBCDA as in Streptococcus pneumoniae (Zhang et al ., 2020), both proteins have the same name but do not belong to the same protein family.…”

“…Altogether, our results indicate, that PiuA is involved in the uptake of iron by epinephrine, norepinephrine, dopamine, and L-DOPA. PiuA in P. aeruginosa is a TBDT and not a solute binding lipoprotein associated to the ABC transporter PiuBCDA as in Streptococcus pneumoniae (Zhang et al, 2020), both proteins have the same name but to not belong to the same protein family.…”

“…At last, more recently, it was shown that the solute binding lipoprotein PiuA from the Fe acquisition ABC transporter PiuBCDA, binds tetradentate norepinephrine-Fe complexes, (Zhang et al, 2020).…”

“…In addition, the enterohemorrhagic strain of Escherichia coli O157:H7 is able to sense the presence of epinephrine and norepinephrine in its environment through the QseC/B two‐component system involved in quorum sensing (Hughes et al ., 2009) and displays increased iron acquisition in the presence of both norepinephrine and transferrin (Freestone et al ., 2003). At last, more recently, it was shown that the solute binding lipoprotein PiuA from the Fe acquisition ABC transporter PiuBCDA binds tetradentate norepinephrine‐Fe complexes (Zhang et al ., 2020).…”

Discovery and structure of a widespread bacterial ABC transporter specific for ergothioneine

“…Bacterial cell pellets for LMW thiol profiling were prepared by inoculating selected strains in BHI medium under microaerophilic conditions with 5% CO 2 at 37 °C as described in our previous work 86 . In a chemically defined medium (CDM) 87,88 , cells were grown in triplicate in the same condition with or without addition of ET to the indicated concentration (0, 0.05, 0.5, 5 μM).…”