Volume 272, Number 4,
Issue of January 24, 1997
pp. 2056-2059
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
COMMUNICATION:
Structural Determinants for Interaction with Three Different
Effectors on the G Protein 
Subunit
(Received for publication, October 30, 1996, and in revised form, November 19, 1996)
Kang
Yan
and
Narasimhan
Gautam
§
From the Department of 
Anesthesiology and
§ Genetics, Washington University School of Medicine,
St. Louis, Missouri 63110
In the yeast two-hybrid system, a 100-residue
fragment (
1A) from the N terminus of the 1 subunit interacts with
domains specific to adenylyl cyclase 2 (AC2), the muscarinic atrial
potassium channel (GIRK1), and phospholipase C-2 (PLC-2). Based
on the crystal structure of the G protein, 1A is composed of an
N-terminal 
helix, a loop, and five strands in which the
C-terminal four strands form a sheet, the first of seven sheets
that make up the propeller structure of the subunit. A mutant of
1A (L4P, L7P, and L14P), in which the helix was potentially
destroyed, interacted poorly with the G protein 
subunit but
effectively with domains of AC2, GIRK1, and PLC-2. In contrast,
another mutant of 1A (S72A, D76A, and W82A), in which a network of
hydrogen bonds was disrupted, interacted poorly with GIRK1 and PLC-2
domains, but effectively with the subunit and the AC2 domain. These
results suggest that the proper folding of the first five strands
in the G protein subunit is a requirement for appropriately
positioning residues that interact with GIRK1 and PLC-2.
Furthermore, since mutations that potentially disrupted the folding of
these strands did not affect interaction with AC2, the structural
determinants on the G protein subunit for interaction with various
effectors may be different.
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