Why transport matters: an update on carrier proteins in Apicomplexan parasites

The movement of molecules across the membranous barriers of a cell is fundamental to cellular homeostasis in every living organism. This vital process is facilitated through a mechanistically diverse class of proteins, collectively known as membrane transporters. Among these are so-called carrier proteins that can function in passive and active transport mechanisms. They exhibit high substrate specificity and undergo conformational changes to transfer a specific solute across the membrane, thereby facilitating diffusion or actively transporting a molecule under energy expenditure or against an established electrochemical gradient. Apicomplexan parasites invest up to 5% of their genome to encode for membrane transporters; however, only a few have been fully characterised, and their specific mechanisms remain largely unknown. Recent advances in structural biology and the application of state-of-the-art genomic editing tools have greatly accelerated investigations into the intricate mechanisms of Apicomplexan carrier proteins. Understanding the molecular ‘ins and outs’ of membrane transporters is fundamental to inform the rational design of inhibitors, as well as to overcome antimicrobial resistance.