Crystallization and preliminary X-ray analysis of pseudo-merohedrally twinned crystals of the full-length β2 subunit of the Kv1 K + channel from Rattus norvegicus

Abstract

The eukaryotic Kv1 voltage-gated K+ channel is composed of four α subunits and four β subunits. The full-length β2 subunit from Rattus norvegicus has been expressed in Esherichia coli, purified and then crystallized. A careful molecular-replacement study using the structure of the truncated β2 subunit reveals that the crystals are perfectly pseudo-merohedrally twinned. While the apparent space group of the crystals was P4212, the real space group was shown to be P2 1212, with unit-cell parameters a = 222.6, b = 222.6, c = 82.3 Å. An asymmetric unit of the crystal contains two β2 tetramers (MW = 340 kDa). A data set was collected from a crystal to 2.0 Å resolution, with 266 659 independent observations (93.0% complete) and R merge = 0.06. Although the crystals are perfectly twinned, they are still suitable for structural determination by molecular replacement using the truncated β2-subunit structure. © 2004 International Union of Crystallography. Printed in Denmark - all rights reserved.