The structure of the prokaryotic cyclic nucleotide-modulated potassium channel MloK1 at 16 A resolution.
The gating ring of cyclic nucleotide-modulated channels is proposed to be either a two-fold symmetric dimer of dimers or a four-fold symmetric tetramer based on high-resolution structure data of soluble cyclic nucleotide-binding domains and functional data on intact channels. We addressed this controversy by obtaining structural data on an intact, full-length, cyclic nucleotide-modulated potassium channel, MloK1, from Mesorhizobium loti, which also features a putative voltage-sensor. We present here the 3D single-particle structure by transmission electron microscopy and the projection map of membrane-reconstituted 2D crystals of MloK1 in the presence of cAMP. Our data show a four-fold symmetric arrangement of the CNBDs, separated by discrete gaps. A homology model for full-length MloK1 suggests a vertical orientation for the CNBDs. The 2D crystal packing in the membrane-embedded state is compatible with the S1-S4 domains in the vertical "up" state.
Chiu
Po-Lin
PL
Molecular and Cellular Biology, College of Biological Sciences, University of California-Davis, 1 Shields Avenue, Davis, CA 95616, USA.
Pagel
Matthew D
MD
Evans
James
J
Chou
Hui-Ting
HT
Zeng
Xiangyan
X
Gipson
Bryant
B
Stahlberg
Henning
H
Nimigean
Crina M
CM
D000595:Amino Acid Sequence; D003461:Crystallography; D000242:Cyclic AMP / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000737:chemistry*; D011487:Protein Conformation; D012231:Rhizobium / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
D015221:Potassium Channels; D000242:Cyclic AMP