Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 110, Issue 19, Pages 7696-7701Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1218986110
Keywords
major facilitator superfamily; LeuT-fold transporters; ABC transporters; neurotransmitter transporters
Categories
Funding
- National Science Foundation's Extreme Science and Engineering Discovery Environment (XSEDE) Resources Grant [MCA06N060]
- Anton at Pittsburg Supercomputing Center [MCB100017P]
- National Institutes of Health [R01-GM086749, U54-GM087519, P41-GM104601]
Ask authors/readers for more resources
Membrane transporters rely on highly coordinated structural transitions between major conformational states for their function, to prevent simultaneous access of the substrate binding site to both sides of the membrane-a mode of operation known as the alternating access model. Although this mechanism successfully accounts for the efficient exchange of the primary substrate across the membrane, accruing evidence on significant water transport and even uncoupled ion transport mediated by transporters has challenged the concept of perfect mechanical coupling and coordination of the gating mechanism in transporters, which might be expected from the alternating access model. Here, we present a large set of extended equilibrium molecular dynamics simulations performed on several classes of membrane transporters in different conformational states, to test the presence of the phenomenon in diverse transporter classes and to investigate the underlying molecular mechanism of water transport through membrane transporters. The simulations reveal spontaneous formation of transient water-conducting (channel-like) states allowing passive water diffusion through the lumen of the transporters. These channel-like states are permeable to water but occluded to substrate, thereby not hindering the uphill transport of the primary substrate, i.e., the alternating access model remains applicable to the substrate. The rise of such water-conducting states during the large-scale structural transitions of the transporter protein is indicative of imperfections in the coordinated closing and opening motions of the cytoplasmic and extracellular gates. We propose that the observed water-conducting states likely represent a universal phenomenon in membrane transporters, which is consistent with their reliance on large-scale motion for function.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available