Biologically active two-dimensional crystals of aquaporin CHIP

T. Walz, B. L. Smith, M. L. Zeidel, A. Engel, P. Agre

Research output: Contribution to journalArticlepeer-review

182 Scopus citations


Plasma membranes of several mammalian tissues are highly permeable to water due to the presence of CHIP, the 28-kDa channel-forming integral protein which is the archetypal member of the aquaporin family of water channel proteins. To define its native structure, purified red cell CHIP protein was reconstituted into lipid bilayers at a high protein-to-lipid ratio, and the resulting 3-μm diameter membrane vesicles were examined by high resolution electron microscopy. The reconstituted membranes contained highly ordered two-dimensional crystalline lattices of p4221 symmetry in which each CHIP tetramer contained a central depression extending from the outer and inner surfaces of the membrane into the transbilayer domain of the molecule. The reconstituted membranes also exhibited extremely high osmotic water permeability, P(f) = 0.472 cm/s, corresponding to the sum of activities of all incorporated CHIP molecules. These studies report the first two- dimensional crystallization of a biologically active water channel and provide direct evidence of the structure responsible for its pore-like behavior.

Original languageEnglish (US)
Pages (from-to)1583-1586
Number of pages4
JournalJournal of Biological Chemistry
Issue number3
StatePublished - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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