Scope
By convention of the nomenclature system, members within an individual SLC family have greater than 20-25% sequence homology to each other. In contrast, the homology between SLC families is very low to non-existent. Hence, the criteria for inclusion of a family into the SLC group is not evolutionary relatedness to other SLC families but rather functional (i.e., an integral membrane protein that transports a solute).
The SLC group include examples of transport proteins that are:
- facilitative transporters (allow solutes to flow downhill with their electrochemical gradients)
- secondary active transporters (allow solutes to flow uphill against their electrochemical gradient by coupling to transport of a second solute that flows downhill with its gradient such that the overall free energy change is still favorable)
The SLC series does not include members of transport protein families that have previously been classified by other widely accepted nomenclature systems including:
- primary active transporters (allow flow uphill against electrochemical gradients) such as ABC (ATP Binding Cassette) transporters by coupling transport to an energy releasing event such as ATP hydrolysis
- ion channels
- aquaporins (water channels)
Read more about this topic: Solute Carrier Family
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