Solute carrier (SLC) family members are membrane proteins that facilitate the transport of a wide array of substrates across membranes. SLCs may be either passive facilitative transporters (uniporters), transporting a substrate down its electrochemical gradient, or secondary active transporters, coupling the transport of substrates against their electrochemical gradients with the transport of other substrates down their electrochemical gradients. Secondary active transporters may act as symporters, transporting substrates in the same direction, or antiporters, transporting substrates in opposite directions. (Adapted from PMID:31214990, PMID:32810346, FBrf0234984 and FBrf0226917).