TY  - JOUR
AU  - Schirmeyer, Jana
AU  - Hummert, Sabine
AU  - Eick, Thomas
AU  - Schulz, Eckhard
AU  - Schwabe, Tina
AU  - Ehrlich, Gunter
AU  - Kukaj, Taulant
AU  - Wiegand, Melanie
AU  - Sattler, Christian
AU  - Schmauder, Ralf
AU  - Zimmer, Thomas
AU  - Kosmalla, Nisa
AU  - Münch, Jan
AU  - Bonus, Michele
AU  - Gohlke, Holger
AU  - Benndorf, Klaus
TI  - Thermodynamic profile of mutual subunit control in a heteromeric receptor
JO  - Proceedings of the National Academy of Sciences of the United States of America
VL  - 118
IS  - 30
SN  - 1091-6490
CY  - Washington, DC
PB  - National Acad. of Sciences
M1  - FZJ-2021-03098
SP  - e2100469118
PY  - 2021
AB  - Cyclic nucleotide-gated (CNG) ion channels of olfactory neurons are tetrameric membrane receptors that are composed of two A2 subunits, one A4 subunit, and one B1b subunit. Each subunit carries a cyclic nucleotide-binding domain in the carboxyl terminus, and the channels are activated by the binding of cyclic nucleotides. The mechanism of cooperative channel activation is still elusive. Using a complete set of engineered concatenated olfactory CNG channels, with all combinations of disabled binding sites and fit analyses with systems of allosteric models, the thermodynamics of microscopic cooperativity for ligand binding was subunit- and state-specifically quantified. We show, for the closed channel, that preoccupation of each of the single subunits increases the affinity of each other subunit with a Gibbs free energy (ΔΔG) of ∼−3.5 to ∼−5.5 kJ ⋅ mol−1, depending on the subunit type, with the only exception that a preoccupied opposite A2 subunit has no effect on the other A2 subunit. Preoccupation of two neighbor subunits of a given subunit causes the maximum affinity increase with ΔΔG of ∼−9.6 to ∼−9.9 kJ ⋅ mol−1. Surprisingly, triple preoccupation leads to fewer negative ΔΔG values for a given subunit as compared to double preoccupation. Channel opening increases the affinity of all subunits. The equilibrium constants of closed–open isomerizations systematically increase with progressive liganding. This work demonstrates, on the example of the heterotetrameric olfactory CNG channel, a strategy to derive detailed insights into the specific mutual control of the individual subunits in a multisubunit membrane receptor.
LB  - PUB:(DE-HGF)16
C6  - 34301910
UR  - <Go to ISI:>//WOS:000685039000028
DO  - DOI:10.1073/pnas.2100469118
UR  - https://juser.fz-juelich.de/record/894207
ER  -