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Periplasmic Binding Protein YiuA Enables Yersinia pestis to Scavenge Fe(III)-Catechol Siderophores
Emil Thomsen1, Parker Stow1, Daniel Roth1
1Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106-9510, United States.
Abstract:
Yersinia pestis, the pathogen causing plague, requires iron to grow. Y. pestis employs several uptake pathways for iron, including the siderophore yersiniabactin, as well as hemin and inorganic iron. The Y. pestis iron assimilation repertoire further harbors the uncharacterized YiuRABC pathway, presumed to transport an unidentified Fe(III)-siderophore(s). Through intrinsic fluorescence quenching of the periplasmic binding protein YiuA, we discovered that YiuA displays high affinity toward Fe(III) complexes of the hydrolysis products of enterobactin, Fe(III)-[di(DHB-LSer)] and Fe(III)-[DHB-LSer]2, with Kd values of 27.6 ± 4.2 nM and 28.2 ± 6.9 nM, respectively, as well as the bis-catechol siderophore butanochelin, with Kd 0.76 ± 0.17 nM. By comparison, YiuA has a much weaker affinity for intact Fe(III)-enterobactin, Kd 444.7 ± 20.6 nM. Electronic circular dichroism spectroscopy reveals YiuA has a strong preference for binding Λ configured Fe(III)-siderophores, which can be achieved with the Fe(III) bis-catechol complexes but not Fe(III)-enterobactin.
Insights
Yersinia pestis uses the YiuRABC pathway to acquire iron. The YiuA protein binds specific iron-siderophore complexes, including butanochelin, crucial for plague pathogen growth.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- * Yersinia pestis, the causative agent of plague, has a critical requirement for iron for its growth and survival.
- * Y. pestis utilizes multiple iron uptake systems, including yersiniabactin, hemin, and inorganic iron.
- * The YiuRABC pathway is a poorly understood iron assimilation system in Y. pestis, hypothesized to transport unknown Fe(III)-siderophore complexes.
Purpose of the Study:
- * To characterize the substrate specificity and binding properties of the YiuA protein within the YiuRABC pathway.
- * To elucidate the role of YiuA in the iron assimilation strategy of Yersinia pestis.
- * To investigate the structural preferences of YiuA for Fe(III)-siderophore binding.
Main Methods:
- * Intrinsic fluorescence quenching assays were employed to measure the binding affinity of YiuA to various Fe(III)-siderophore complexes.
- * Electronic circular dichroism (ECD) spectroscopy was utilized to determine the stereochemical preferences of YiuA binding.
- * Synthesis and characterization of Fe(III)-siderophore hydrolysis products and complexes were performed.
Main Results:
- * YiuA exhibits high affinity for Fe(III)-[di(2,3-dihydroxybenzoyl)-L-serine] (Fe(III)-[di(DHB-LSer)]) and Fe(III)-[2,3-dihydroxybenzoyl-L-serine]2 (Fe(III)-[DHB-LSer]2), with Kd values of 27.6 ± 4.2 nM and 28.2 ± 6.9 nM, respectively.
- * YiuA demonstrates a particularly strong affinity for the bis-catechol siderophore butanochelin (Kd 0.76 ± 0.17 nM).
- * YiuA shows significantly lower affinity for intact Fe(III)-enterobactin (Kd 444.7 ± 20.6 nM) and a preference for Λ-configured Fe(III)-siderophores, achievable with bis-catechol complexes.
Conclusions:
- * The YiuRABC pathway, through the YiuA protein, specifically targets and binds certain Fe(III)-siderophore complexes, including butanochelin and enterobactin hydrolysis products.
- * YiuA's preference for Λ-configured siderophores suggests a stereospecific recognition mechanism in iron uptake.
- * These findings reveal a novel aspect of iron acquisition in Yersinia pestis, potentially impacting virulence and therapeutic strategies.
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