Abstract
Aquaporins (AQPs) are intrinsic membrane proteins that mediate passive bidirectional water transport across cell membranes. The rate of the said water transport varies in different membrane environments, highlighting direct effects of membrane composition. Currently, how membrane lipids directly regulate water transport is unknown. Here, we describe the dynamics and water transport of AQP in 3 different membrane-mimetic nanodiscs (DOPC, 3:1 DOPC: DOPG and E. coli polar lipid) using amide-hydrogen/deuterium exchange mass spectrometry (HDXMS). Our results reveal that membrane composition alters dynamics and modulates water transport of AqpZ. AQP dynamics correlates with water transport showing a bell-shaped curve - higher dynamics increases water transport till a certain limit, after which it inhibits water transport - suggesting that through fine balance between stabilization and fluidity, lipids can function as critical allosteric regulators of water transport across AqpZ. Hence, alteration of protein dynamics - in a membrane composition-dependent manner offers a handle to program water permeability of AqpZ. Our findings revealed a novel lipid-mediated allosteric mechanism of AqpZ, which has tremendous implications on cellular osmoregulation and selection of optimal matrix materials for fabrication of optimal AQP biomimetic membranes.
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