A comparison of electrophysiological properties of the CNGA1, CNGA1tandem and CNGA1cys-free channels.
Three constructs are used for the analysis of biophysical properties of CNGA1 channels: the WT CNGA1 channel, a CNGA1 channel where all endogenous cysteines were removed (CNGA1cys-free) and a construct composed of two CNGA1 subunits connected by a small linker (CNGA1tandem). So far, it has been assumed, but not proven, that the molecular structure of these ionic channels is almost identical. The I/V relations, ionic selectivity to alkali monovalent cations, blockage by tetracaine and TMA+ were not significantly different. The cGMP dose response and blockage by TEA+ and Cd2+ were instead significantly different in CNGA1 and CNGA1cys-free channels, but not in CNGA1 and CNGA1tandem channels. Cd2+ blocked irreversibly the mutant channel A406C in the absence of cGMP. By contrast, Cd2+ did not block the mutant channel A406C in the CNGA1cys-free background (A406Ccys-free), but an irreversible and almost complete blockage was observed in the presence of the cross-linker M-4-M. Results obtained with different MTS cross-linkers and reagents suggest that the 3D structure of the CNGA1cys-free differs from that of the CNGA1 channel and that the distance between homologous residues at position 406 in CNGA1cys-free is longer than in the WT CNGA1 by several Angstroms.
Mazzolini
Monica
M
International School for Advanced Studies, via Beirut 2-4, 34014, Trieste, Italy.
Nair
Anil V
AV
Torre
Vincent
V
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000737:chemistry* / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
C518243:CNGA1 protein, human; D054815:Cyclic Nucleotide-Gated Cation Channels