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TonB-Dependent Heme/Hemoglobin Utilization by Caulobacter crescentus HutA.
Heloise Balhesteros1, Yan Shipelskiy2, Noah J Long2
1Departamento de Microbiologia, Instituto de Ciencias Biomedicas, Universidade de São Paulo, São Paulo, Brazil.
Journal of Bacteriology
|December 30, 2016
Summary
Caulobacter crescentus acquires iron using various siderophores and heme. Researchers identified HutA as the first outer membrane protein crucial for heme and hemoglobin uptake in this bacterium.
Area of Science:
- Microbiology and Molecular Biology
- Bacterial Physiology and Genetics
- Iron Metabolism in Bacteria
Background:
- Caulobacter crescentus possesses numerous putative TonB-dependent transporters (TBDT) with largely unknown functions in iron acquisition.
- Understanding iron uptake mechanisms is crucial for bacterial survival and pathogenesis.
Purpose of the Study:
- To biochemically characterize the iron uptake systems in Caulobacter crescentus.
- To identify novel iron transporters and elucidate their phylogenetic relationships.
- To determine the role of specific TBDTs in iron acquisition.
Main Methods:
- Siderophore nutrition tests using various iron chelates, heme, and hemoglobin.
- Kinetics and thermodynamics studies of iron-citrate and apoferrichrome binding and transport.
- Bioinformatic analysis of Fur-regulated loci and TBDT identification.
- SDS-PAGE and mass spectrometry for TBDT expression analysis.
- Construction and phenotypic analysis of a Δ02277 mutant.
Main Results:
- Caulobacter crescentus utilizes ferric hydroxamate siderophores, hemin, and hemoglobin but not ferrioxamine B or ferric catecholates.
- Transport kinetics for ferrichrome and citrate were determined, showing similarities to E. coli systems.
- Five TBDTs were identified with differential expression under varying iron conditions; TBDT 02277 (designated HutA) was essential for hemin and hemoglobin transport.
Conclusions:
- HutA (TBDT 02277) is the first identified outer membrane protein involved in heme/hemoglobin acquisition by Caulobacter crescentus.
- This study clarifies phylogenetic relationships among C. crescentus TBDTs and identifies key players in iron acquisition.
- The findings provide a foundation for understanding the diverse iron uptake strategies in C. crescentus.
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