Structure of Galpha(i1) bound to a GDP-selective peptide provides insight into guanine nucleotide exchange.
Heterotrimeric G proteins are molecular switches that regulate numerous signaling pathways involved in cellular physiology. This characteristic is achieved by the adoption of two principal states: an inactive, GDP bound state and an active, GTP bound state. Under basal conditions, G proteins exist in the inactive, GDP bound state; thus, nucleotide exchange is crucial to the onset of signaling. Despite our understanding of G protein signaling pathways, the mechanism of nucleotide exchange remains elusive. We employed phage display technology to identify nucleotide state-dependent Galpha binding peptides. Herein, we report a GDP-selective Galpha binding peptide, KB-752, that enhances spontaneous nucleotide exchange of Galpha(i) subunits. Structural determination of the Galpha(i1)/peptide complex reveals unique changes in the Galpha switch regions predicted to enhance nucleotide exchange by creating a GDP dissociation route. Our results cast light onto a potential mechanism by which Galpha subunits adopt a conformation suitable for nucleotide exchange.
Johnston
Christopher A
CA
Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Willard
Francis S
FS
Jezyk
Mark R
MR
Fredericks
Zoey
Z
Bodor
Erik T
ET
Jones
Miller B
MB
Blaesius
Rainer
R
Watts
Val J
VJ
Harden
T Kendall
TK
Sondek
John
J
Ramer
J Kevin
JK
Siderovski
David P
DP
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D015374:Biosensing Techniques; D002021:Buffers; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019281:Dimerization; D004583:Electrons; D004797:Enzyme-Linked Immunosorbent Assay; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry; D006150:Guanine Nucleotides / Q000737:chemistry; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000737:chemistry; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013237:Stereoisomerism; D020349:Surface Plasmon Resonance; D013997:Time Factors
D002021:Buffers; D020662:Guanine Nucleotide Exchange Factors; D006150:Guanine Nucleotides; D009711:Nucleotides; D019151:Peptide Library; D010455:Peptides; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D008274:Magnesium