Cell
Volume 97, Issue 7, 25 June 1999, Pages 943-952
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Article
Structure of a Voltage-Dependent K+ Channel β Subunit

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Abstract

The integral membrane subunits of many voltage-dependent potassium channels are associated with an additional protein known as the β subunit. One function of β subunits is to modify K+ channel gating. We have determined the structure of the conserved core of mammalian β subunits by X-ray crystallography at 2.8 Å resolution. Like the integral membrane component of K+ channels, β subunits form a four-fold symmetric structure. Each subunit is an oxido-reductase enzyme complete with a nicotinamide cofactor in its active site. Several structural features of the enzyme active site, including its location with respect to the four-fold axis, imply that it may interact directly or indirectly with the K+ channel’s voltage sensor. This structure suggests a mechanism for coupling membrane electrical excitability directly to chemistry of the cell.

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