Does human P-glycoprotein efflux involve transmembrane alpha helix breakage?

Abstract

The occluded conformation suggested in a recent article that revealed a new inward-17 facing conformation for the human P-glycoprotein may not represent the closing of a gate region 18 but instead an artifact derived from lateral compression in a too small sized nanodisc, used to 19 stabilize the transmembrane domains of the transporter. 20 21

Active Participation of Membrane Lipids in Inhibition of Multidrug Transporter P-Glycoprotein

“…The zosuquidar-bound cryo-EM structure shows a similar disorder in TM10 in the presence of the inhibitor, 36 although local unfolding in Portal 1 helices (TM4 and TM6) is also observed in this structure. This unfolding of the Portal 1 helices, which is not observed in other Pgp structures, 9,21,22 has been suspected by a recent computational study 65 to be an artifact of the small size of the nanodisc used in structural determination.…”

Active participation of membrane lipids in inhibition of multidrug transporter P-glycoprotein

“…The zosuquidar-bound cryoEM structure shows a similar disorder in TM10 in the presence of the inhibitor, 36 although local unfolding in Portal 1 helices (TM4 and TM6) is also observed in this structure. This unfolding of the Portal 1 helices, which is not observed in other Pgp structures, 9,21,22 has been suspected by a recent computational study 65 to be an artifact of the small size of the nanodisc used in structural determination.…”

Modeling Substrate Entry into the P-Glycoprotein Efflux Pump at the Blood–Brain Barrier

“…During efflux, conformational changes are associated with changes in the aperture angle and NBD spacing. , Structural studies of the inward-facing state have reported NBD spacings in the range of 40–60 Å. − A recent cryo-EM study reported a spacing of ∼30 Å for human P-gp . Recent reviews of the P-gp structure reveal a large heterogeneity, including disparities in aperture angle between the cryo-EM structures and values derived from X-ray crystallography …”

“…12 Recent reviews of the P-gp structure reveal a large heterogeneity, including disparities in aperture angle between the cryo-EM structures and values derived from X-ray crystallography. 13 In vitro studies of P-gp function provide limited mechanistic insight into the steps associated with efflux; however, MD simulations can play an important role in elucidating processes not directly accessible by experiment. 15 All-atom MD simulations of large membrane protein systems, such as P-gp, are computationally expensive, and hence, biased sampling strategies are widely used to overcome this challenge.…”