Crystal structure of a yeast aquaporin at 1.15 angstrom reveals a novel gating mechanism.

• Aquaporins are transmembrane proteins that facilitate the flow of water through cellular membranes. An unusual characteristic of yeast aquaporins is that they frequently contain an extended N terminus of unknown function. Here we present the X-ray structure of the yeast aquaporin Aqy1 from Pichia pastoris at 1.15 A resolution. Our crystal structure reveals that the water channel is closed by the N terminus, which arranges as a tightly wound helical bundle, with Tyr31 forming H-bond interactions to a water molecule within the pore and thereby occluding the channel entrance. Nevertheless, functional assays show that Aqy1 has appreciable water transport activity that aids survival during rapid freezing of P. pastoris. These findings establish that Aqy1 is a gated water channel. Mutational studies in combination with molecular dynamics simulations imply that gating may be regulated by a combination of phosphorylation and mechanosensitivity.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

Aquaporins

chemistry

metabolism

Biological Transport

Computer Simulation

Crystallography

X-Ray

Freezing

Ion Channel Gating

Microbial Viability

Models

Molecular

Phosphorylation

Pichia

chemistry

Protein Structure

Secondary

Spinacia oleracea

chemistry

Structural Homology

Protein

Tyrosine

metabolism

Water

Freezing

Publication and Content Type

ref (subject category)

art (subject category)