Related Experiment Videos
ABC transporters: one, two or four extracytoplasmic substrate-binding sites?
Tiemen van der Heide1, Bert Poolman
1Department of Biotehnology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands.
Abstract:
Two families of ATP-binding cassette (ABC) transporters in which one or two extracytoplasmic substrate-binding domains are fused to either the N- or C-terminus of the translocator protein have been detected. This suggests that two, or even four, substrate-binding sites may function in the ABC transporter complex. This domain organization in ABC transporters, widely represented among microorganisms, raises new possibilities for how the substrate-binding protein(s) (SBPs) might interact with the translocator. One appealing hypothesis is that multiple substrate-binding sites in proximity to the entry site of the translocation pore enhance the transport capacity. We also discuss the implications of multiple substrate-binding sites in close proximity to the translocator in terms of broadened substrate specificity and possible cooperative interactions between SBPs and the translocator.
Insights
Two families of ATP-binding cassette (ABC) transporters feature fused substrate-binding domains, suggesting multiple binding sites. This organization may enhance transport capacity and specificity in microbial systems.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- ATP-binding cassette (ABC) transporters are crucial for cellular transport.
- Domain organization in ABC transporters can vary, impacting function.
- Extracytoplasmic substrate-binding domains fused to translocator proteins represent a distinct structural class.
Purpose of the Study:
- To investigate the functional implications of fused extracytoplasmic substrate-binding domains in ABC transporters.
- To explore how this domain organization affects substrate binding and transport.
- To propose hypotheses regarding the interaction between substrate-binding proteins (SBPs) and translocators.
Main Methods:
- Bioinformatic analysis of ABC transporter structures.
- Comparative genomics to identify domain fusions.
- Hypothetical modeling of protein-protein interactions.
Main Results:
- Identification of two ABC transporter families with fused N- or C-terminal substrate-binding domains.
- Postulation of up to four functional substrate-binding sites per complex.
- Observation that this organization is prevalent in microorganisms.
Conclusions:
- Fused domain organization in ABC transporters offers novel mechanisms for substrate interaction.
- Multiple substrate-binding sites near the translocation pore may enhance transport efficiency.
- This structural arrangement could lead to broadened substrate specificity and cooperative SBP-translocator interactions.