Unraveling the Membrane Topology of TMEM151A: A Step Towards Understanding its Cellular Role.

Transmembrane protein 151A (TMEM151A) has been identified as a causative gene for paroxysmal kinesigenic dyskinesia, though its molecular function remains almost completely unknown. Understanding the membrane topology of transmembrane proteins is crucial for elucidating their functions and possible interacting partners. In this study, we utilized molecular dynamics simulations, immunocytochemistry, and electron microscopy to define the topology of TMEM151A. Our results validate a starting AlphaFold model of TMEM151A and reveal that it comprises a transmembrane domain with two membrane-spanning alpha helices connected by a short extracellular loop and an intramembrane helix-hinge-helix structure. Notably, most of the protein is oriented towards the intracellular side of the membranes with a large cytosolic domain featuring a combination of alpha-helix and beta-sheet structures, as well as the protein N- and C-termini. These insights into TMEM151A's topology and orientation of its domains with respect of the cell membranes provide essential information for future functional studies and represent a first fundamental step for understanding its role in the pathogenesis of paroxysmal kinesigenic dyskinesia.