Structural determinants for interaction with three different effectors on the G protein beta subunit.
In the yeast two-hybrid system, a 100-residue fragment (beta1A) from the N terminus of the beta1 subunit interacts with domains specific to adenylyl cyclase 2 (AC2), the muscarinic atrial potassium channel (GIRK1), and phospholipase C-beta2 (PLC-beta2). Based on the crystal structure of the G protein, beta1A is composed of an N-terminal alpha helix, a loop, and five beta strands in which the C-terminal four beta strands form a beta sheet, the first of seven sheets that make up the propeller structure of the beta subunit. A mutant of beta1A (L4P, L7P, and L14P), in which the alpha helix was potentially destroyed, interacted poorly with the G protein gamma subunit but effectively with domains of AC2, GIRK1, and PLC-beta2. In contrast, another mutant of beta1A (S72A, D76A, and W82A), in which a network of hydrogen bonds was disrupted, interacted poorly with GIRK1 and PLC-beta2 domains, but effectively with the gamma subunit and the AC2 domain. These results suggest that the proper folding of the first five beta strands in the G protein beta subunit is a requirement for appropriately positioning residues that interact with GIRK1 and PLC-beta2. Furthermore, since mutations that potentially disrupted the folding of these beta strands did not affect interaction with AC2, the structural determinants on the G protein beta subunit for interaction with various effectors may be different.
Yan
K
K
Department of, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Gautam
N
N
D000262:Adenylyl Cyclases / Q000378:metabolism; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019204:GTP-Binding Proteins / Q000737:chemistry*; D020962:Heterotrimeric GTP-Binding Proteins; D007527:Isoenzymes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D054799:Phospholipase C beta; D015221:Potassium Channels / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D029702:Schizosaccharomyces pombe Proteins; D010738:Type C Phospholipases / Q000378:metabolism
D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D007527:Isoenzymes; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D029702:Schizosaccharomyces pombe Proteins; C101525:git5 protein, S pombe; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins; D000262:Adenylyl Cyclases; C100622:adenylyl cyclase 2