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ABC transporter for corrinoids in Halobacterium sp. strain NRC-1
Jesse D Woodson1, April A Reynolds, Jorge C Escalante-Semerena
1Department of Bacteriology, University of Wisconsin, 144A Enzyme Institute, 1710 University Avenue, Madison, WI 53726-4087, USA.
Journal of Bacteriology
|August 20, 2005
Summary
Researchers identified a novel ABC transporter system in Halobacterium sp. strain NRC-1 responsible for cobalamin (vitamin B12) uptake. This archaeal corrinoid transport system is crucial for nutrient acquisition in extreme environments.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Corrinoid utilization is essential for many organisms, but the transport mechanisms in archaea remain largely uncharacterized.
- Halobacterium sp. strain NRC-1 is an extremophilic archaeon with unique metabolic capabilities.
Purpose of the Study:
- To investigate the genetic basis of corrinoid (cobalamin) transport in the halophilic archaeon Halobacterium sp. strain NRC-1.
- To identify and characterize the components of a putative ABC transporter involved in cobalamin uptake.
Main Methods:
- Genetic analysis of Halobacterium sp. strain NRC-1 using mutant strains with lesions in specific open reading frames (ORFs).
- Nutritional analyses to determine cobalamin requirements for growth.
- Bioassays to detect cobalamin presence in cell extracts.
Main Results:
- Mutants in Vng1370G, Vng1371Gm, and Vng1369G ORFs exhibited a 10^5-fold higher requirement for cobalamin, indicating their role in its transport.
- These ORFs were identified as orthologs of bacterial cobalamin ABC transporter components: BtuC (permease), BtuD (ATPase), and BtuF (substrate-binding protein).
- Evidence suggests BtuF is extracellularly located for cobalamin binding, while BtuCD form the membrane-associated complex. Regulation of corrinoid transport and biosynthesis was also observed.
Conclusions:
- The study provides the first genetic evidence for an ABC transporter system mediating cobalamin uptake in an archaeon.
- The identified BtuC, BtuD, and BtuF proteins function as a complex for corrinoid utilization in Halobacterium sp. strain NRC-1.
- These findings advance our understanding of nutrient transport mechanisms in extremophilic archaea.