| Type: | Family | Name: | Arf GTPase activating protein |
| Description: | This entry describes a family of small GTPase activating proteins, for example ARF1-directed GTPase-activating protein, the cycle control GTPase activating protein (GAP) GCS1 which is important for the regulation ofthe ADP ribosylation factor ARF, a member of the Ras superfamily of GTP-binding proteins []. The GTP-bound form of ARF is essential for the maintenance of normalGolgi morphology, it participates in recruitment of coat proteins which are required for budding and fission of membranes. Before the fusion with anacceptor compartment the membrane must be uncoated. This step required the hydrolysis of GTP associated to ARF. These proteins contain a characteristic zinc finger motif(Cys-x2-Cys-x(16,17)-x2-Cys) which displays some similarity to the C4-type GATA zinc finger. The ARFGAP domain display no obvious similarity to other GAPproteins.The 3D structure of the ARFGAP domain of the PYK2-associated protein beta has been solved []. It consists of a three-stranded beta-sheet surrounded by 5alpha helices. The domain is organised around a central zinc atom which is coordinated by 4 cysteines. The ARFGAP domain is clearlyunrelated to the other GAP proteins structures which are exclusively helical. Classical GAP proteins accelerate GTPase activity by supplying an argininefinger to the active site. The crystal structure of ARFGAP bound to ARF revealed that the ARFGAP domain does not supply an arginine to the active sitewhich suggests a more indirect role of the ARFGAP domain in the GTPase hydrolysis [].The Rev protein of human immunodeficiency virus type 1 (HIV-1) facilitates nuclear export of unspliced and partly-spliced viral RNAs []. Rev containsan RNA-binding domain and an effector domain; the latter is believed to interact with a cellular cofactor required for the Rev response and henceHIV-1 replication. Human Rev interacting protein (hRIP) specifically interacts with the Rev effector. The amino acid sequence of hRIP is characterised by an N-terminal, C-4 class zinc finger motif. | Short Name: | ArfGAP |
