Message hidden in α-helices – towards a better understanding of plant ABCG transporters’ multispecificity

Abstract

ABC transporters are ubiquitous in all organisms and constitute one of the largest protein families. The substantial expansion of this family in plants coincided with the emergence of fundamental novelties that facilitated successful adaptation to a sessile lifestyle on land. It also resulted in selectivity and multispecificity toward endogenous molecules observed for certain ABC transporters. Understanding the molecular determinants behind this intriguing feature remains an ongoing challenge for the functional characterization of these proteins. This review synthesizes current achievements and methodologies that enhance our mechanistic understanding of how ABCG transporters, which are particularly numerous in land plants, specifically recognize and transport endogenous compounds. We examine in silico modeling and the recent advancements in the structural biology of ABCGs. Furthermore, we highlight internal and external factors that potentially influence the substrate selectivity of those proteins. Ultimately, this review contributes to rationalizing our current capacity to fully understand how plants orchestrate membrane transport fulfilled by these proteins.