Biochemical studies of the mechanism of action of the Cdc42-GTPase-activating protein.
J Biol Chem
; 273(26): 16210-5, 1998 Jun 26.
Article
en En
| MEDLINE
| ID: mdl-9632678
The small GTP-binding proteins Rac, Rho, and Cdc42 were shown to mediate a variety of signaling pathways including cytoskeletal rearrangements, cell-cycle progression, and transformation. Key to the proper function of these GTP-binding proteins is an efficient shut-off mechanism that ensures the decay of the signal. Regulatory proteins termed GAPs (GTPase-activating proteins) enhance the intrinsic GTP hydrolysis of the GTP-binding proteins, thereby ensuring signal termination. We have used site-specific mutagenesis to elucidate the limit domain for GAP activity in Cdc42-GAP, and show that in addition to the known GAP-homology domain (three conserved boxes), a C-terminal region outside that domain is also essential for GAP activity. In addition, we have replaced the conserved arginine (Arg305), which was suggested by structural studies to be a key catalytic residue, with an alanine and found that the R305A Cdc42-GAP mutant has a greatly diminished catalytic capacity but is still able to bind Cdc42 with high affinity. Thus, a key catalytic role for this residue is confirmed. However, we also present evidence for the involvement of an additional residue(s), since the R305A Cdc42-GAP mutant still exhibits measurable activity. Some of this residual activity might result from a neighboring arginine, since a double mutant R305A/R306A shows a further decrease in catalytic activity.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas
/
Proteínas ras
/
Proteínas de Ciclo Celular
/
Proteínas de Unión al GTP
/
GTP Fosfohidrolasas
Límite:
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
1998
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos