Binding of the G protein βγ subunit to multiple regions of G protein-gated inward-rectifying K + channels
Abstract
We have previously shown that direct binding of the βγ subunit of G protein (Gβγ) to both the N-terminal domain and the C-terminal domain of a cloned G protein-gated inward-rectifying K + channel subunit, GIRK1, is important for channel activation. We have now further localized the Gβγ binding region in the N-terminal domain of GIRK1 to amino acids 34–86 and the Gβγ binding region in the C-terminal domain of GIRK1 to two separate fragments of amino acids 318–374 and amino acids 390–462. Of the four cloned mammalian GIRK subunits, GIRK1–4, GIRK1 and 4 form heteromeric K + channels in the heart and similar channels in the brain include heteromultimers of GIRK1 and 2, and possibly other GIRK homomultimers and heteromultimers. We found that the N-terminal and the C-terminal domains of all four GIRKs bound Gβγ. The Gβγ binding activities for the C-terminal domains of GIRK2–4 were lower than that for the C-terminal domain of GIRK1. The higher Gβγ binding activity for the C-terminal domain of GIRK1 is due to amino acids 390–462 which are unique to GIRK1. We also found that the N-terminal and C-terminal domains of GIRKs interacted with each other, and the N-terminal domain of either GIRK1 or GIRK4 together with the C-terminal domain of GIRK1 exhibited much enhanced binding of Gβγ. These results are consistent with the idea that the N- and C-terminal domains of the cardiac G protein-gated K + channel subunits may interact with each other to form higher affinity binding site(s) for Gβγ.
- Publication:
-
FEBS Letters
- Pub Date:
- January 1997
- DOI:
- 10.1016/S0014-5793(97)00197-X
- Bibcode:
- 1997FEBSL.405..291H
- Keywords:
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- Direct protein-protein interaction;
- Weaver mutation;
- G-protein-gated inwardly rectifying K + channel;
- Fusion protein;
- Gβγ binding;
- Glutathione- S-transferase