Movements of native C505 during channel gating in CNGA1 channels

• Published in: European biophysics journal Vol. 38; no. 4; pp. 465 - 478
• Main Authors: Nair, Anil V, Anselmi, Claudio, Mazzolini, Monica
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.04.2009; Springer-Verlag; Springer Nature B.V
• Subjects: Amino Acid Sequence; Amino acids; Animals; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Cadmium - metabolism; Cadmium - pharmacology; Cattle; Cell Biology; Cyclic Nucleotide-Gated Cation Channels; Ion Channel Gating; Ion Channels - chemistry; Ion Channels - genetics; Ion Channels - metabolism; Ions; Life Sciences; Membrane Biology; Models, Molecular; Mutants; Mutation; Mutation, Missense; Nanotechnology; Neurobiology; Neurons; Original Paper; Protein Conformation; Protein Structure, Tertiary; Reagents; Studies; Cd; inhibition; CNGA1 channels; S6 domain; Gating; Ionic channels
• ISSN: 0175-7571; 1432-1017
• DOI: 10.1007/s00249-008-0396-7

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. Cd²⁺ (200 μM) inhibited irreversibly mutant channels Q409C and A414C in the closed but not in the open state. Cd²⁺ inhibition was abolished in the mutant A414Ccys₋free, in the double mutant A414C + C505T and in the tandem construct A414C + C505T/CNGA1, but it was present in the construct A414C + C505cys₋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 Cα of C505 in the closed state is located at a distance between 4 and 10.5 Å from the Cα 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 Å from Cα 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.