Structure of the osmo-regulated H2O-channel, AQP-CHIP, in projection at 3.5 A resolution.
An osmo-regulated H2O-channel, aquaporin-CHIP, from bovine red blood cell membranes was purified and reconstituted with lipids, forming two-dimensional crystalline patches that diffract to about 3.0 A resolution. Electron diffraction patterns and high-resolution images of the crystalline patches embedded in glucose were recorded and used to calculate the projection map at 3.5 A resolution. The map confirms that the osmo-regulated H2O-channel basic packing unit is a tetramer and begins to reveal it's structural design. The basic architecture of the H2O-channel protein consists of a trapezoid-like envelope and a substructure located within the trapezoid that could play a crucial role in the channel structure itself; near this substructure there is a region of very low density, which is the probable site of the channel. The trapezoid-like envelope is composed of high density regions many of which can be interpreted as projections of alpha-helices along their axes.
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Life Sciences Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94708, USA.
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D000818:Animals; D051398:Aquaporin 1; D020346:Aquaporins; D002417:Cattle; D003460:Crystallization; D018360:Crystallography, X-Ray; D004134:Dimyristoylphosphatidylcholine; D004910:Erythrocyte Membrane / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry* / Q000302:isolation & purification; D015394:Molecular Structure
D020346:Aquaporins; D007473:Ion Channels; D051398:Aquaporin 1; D004134:Dimyristoylphosphatidylcholine