 Such genetic methods allowed the genetic identification of the "Shaker" K+ channel gene in "Drosophila" before ion channel gene sequences were well known.Study of the altered properties of voltage-gated K+ channel proteins produced by mutated genes has helped reveal the functional roles of K+ channel protein domains and even individual amino acids within their structures.Typically, vertebrate voltage-gated K+ channels are tetramers of four identical subunits arranged as a ring, each contributing to the wall of the trans-membrane K+ pore.