title: Distinct properties of glycine receptor β+/α- interface: unambiguously characterizing heteromeric interface reconstituted in homomeric protein.
abstract: The glycine receptor (GlyR) exists either in homomeric α or heteromeric αβ forms. Its agonists bind at extracellular subunit interfaces. Unlike subunit interfaces from the homomeric α GlyR, subunit interfaces from the heteromeric αβ GlyR have not been characterized unambiguously because of the existence of multiple types of interface within single receptors. Here, we report that, by reconstituting β+/α- interfaces in a homomeric GlyR (αChb+a- GlyR), we were able to functionally characterize the αβ GlyR β+/α- interfaces. We found that the β+/α- interface had a higher agonist sensitivity than that of the α+/α- interface. This high sensitivity was contributed primarily by loop A. We also found that the β+/α- interface differentially modulates the agonist properties of glycine and taurine. Using voltage clamp fluorometry, we found that the conformational changes induced by glycine binding to the β+/α- interface were different from those induced by glycine binding to the α+/α- interface in the α GlyR. Moreover, the distinct conformational changes found at the β+/α- interface in the αChb+a- GlyR were also found in the heteromeric αβ GlyR, which suggests that the αChb+a- GlyR reconstitutes structural components and recapitulates functional properties, of the β+/α- interface in the heteromeric αβ GlyR. Our investigation not only provides structural and functional information about the GlyR β+/α- interface, which could direct GlyR β+/α- interface-specific drug design, but also provides a general methodology for unambiguously characterizing properties of specific protein interfaces from heteromeric proteins.
authors.affiliation: Brain and Mind Research Institute, University of Sydney, Sydney, New South Wales 2050, Australia. qshan@yahoo.com
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shan
authors.forename: Lu
authors.initials: L
authors.lastname: Han
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Lynch
mesh_terms: D000818:Animals; D005998:Glycine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D018009:Receptors, Glycine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
chemical_list: C114561:GLRB protein, human; D018009:Receptors, Glycine; D005998:Glycine