Movements of native C505 during channel gating in CNGA1 channels.
We investigated conformational changes occurring in the C-linker and cyclic nucleotide-binding (CNB) domain of CNGA1 channels by analyzing the inhibition induced by thiol-specific reagents in mutant channels Q409C and A414C in the open and closed state. Cd(2+) (200 microM) inhibited irreversibly mutant channels Q409C and A414C in the closed but not in the open state. Cd(2+) inhibition was abolished in the mutant A414C(cys-free), in the double mutant A414C + C505T and in the tandem construct A414C + C505T/CNGA1, but it was present in the construct A414C + C505(cys-free). The cross-linker reagent M-2-M inhibited mutant channel Q409C in the open state. M-2-M inhibition in the open state was abolished in the double mutant Q409C + C505T and in the tandem construct Q409C + C505T/CNGA1. These results show that C(alpha) of C505 in the closed state is located at a distance between 4 and 10.5 A from the C(alpha) of A414 of the same subunit, but in the open state C505 moves towards Q409 of the same subunit at a distance that ranges from 10.5 to 12.3 A from C(alpha) of this residue. These results are not consistent with a 3-D structure of the CNGA1 channel homologous to the structure of HCN2 channels either in the open or in the closed state.
Nair
Anil V
AV
SISSA, International School for Advanced Studies, Neurobiology Sector, Area Science Park, Edificio Q1, SS 14 Km 163,5, 34012, Basovizza (TS), Italy.
Anselmi
Claudio
C
Mazzolini
Monica
M
D000595:Amino Acid Sequence; D000818:Animals; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology; D002417:Cattle; D054815:Cyclic Nucleotide-Gated Cation Channels; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D020125:Mutation, Missense; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
C475741:CNGA1 protein, bovine; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D002104:Cadmium