About SLC / Solute Carrier Family:
The solute carrier family is a collection of membrane transport proteins. In total, there are some 66 families in the group, which has more than 400 members. You’ll find the majority of the solute carrier family group in the cell membrane.
SLC Function
Their job is to encode membrane-bound transporters. The protein-coding genes fulfil a variety of functions, including the passive transporters, symporters, and antiporters. They’re present in the majority of organic and cellular membranes, though it has not yet been confirmed whether they’re found in the nuclear membrane.
Solute Carrier Family Structure
The system was first developed by the HUGO Gene Nomenclature Committee. To be included in the family, the members must have more than 25% sequence identity to each other. With that being said, there are significant differences between members of the family, too -- for instance, the homology between members is low or non-existent. There are transporters that exist for all endogenous substrates, though in other items, such as non-essential metal and drug antioxidants, the dominant theory suggests that they don’t transport themselves, but rather, hitchhike on others.
While the solute carrier family is extensive, there are some areas where they do not apply. For instance, members of the transport protein families that were previously classified as belonging to other nomenclature systems, such as primary active transporters, ion channels, and aquaporins, are exempt, even if they broadly fulfil the same function. There remain many unanswered questions about the solute carrier family, because it has been a long time since anyone has tried to create an overview map.