Crystal structure of the rac activator, Asef, reveals its autoinhibitory mechanism.
The Rac-specific guanine nucleotide exchange factor (GEF) Asef is activated by binding to the tumor suppressor adenomatous polyposis coli mutant, which is found in sporadic and familial colorectal tumors. This activated Asef is involved in the migration of colorectal tumor cells. The GEFs for Rho family GTPases contain the Dbl homology (DH) domain and the pleckstrin homology (PH) domain. When Asef is in the resting state, the GEF activity of the DH-PH module is intramolecularly inhibited by an unidentified mechanism. Asef has a Src homology 3 (SH3) domain in addition to the DH-PH module. In the present study, the three-dimensional structure of Asef was solved in its autoinhibited state. The crystal structure revealed that the SH3 domain binds intramolecularly to the DH domain, thus blocking the Rac-binding site. Furthermore, the RT-loop and the C-terminal region of the SH3 domain interact with the DH domain in a manner completely different from those for the canonical binding to a polyproline-peptide motif. These results demonstrate that the blocking of the Rac-binding site by the SH3 domain is essential for Asef autoinhibition. This may be a common mechanism in other proteins that possess an SH3 domain adjacent to a DH-PH module.
Murayama
Kazutaka
K
Tohoku University Biomedical Engineering Research Organization, Sendai 980-8575; RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Shirouzu
Mikako
M
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Kawasaki
Yoshihiro
Y
Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0033, and the.
Kato-Murayama
Miyuki
M
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Hanawa-Suetsugu
Kyoko
K
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Sakamoto
Ayako
A
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Katsura
Yasuhiro
Y
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Suenaga
Atsushi
A
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Toyama
Mitsutoshi
M
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Terada
Takaho
T
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Taiji
Makoto
M
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045.
Akiyama
Tetsu
T
Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0033, and the.
Yokoyama
Shigeyuki
S
RIKEN Genomic Sciences Center, Yokohama Institute, Yokohama 230-0045; Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033 Japan. Electronic address: yokoyama@biochem.s.u-tokyo.ac.jp.
D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D002465:Cell Movement; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009154:Mutation; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D040681:Structural Homology, Protein; D020663:ras Guanine Nucleotide Exchange Factors / Q000378:metabolism; D018909:src Homology Domains
C576602:ARHGEF4 protein, human; D025601:Adenomatous Polyposis Coli Protein; D020662:Guanine Nucleotide Exchange Factors; C057811:MCF2 protein, human; D010455:Peptides; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D020663:ras Guanine Nucleotide Exchange Factors; C011083:polyproline