GTPase-activating protein (GAP) for the ADP ribosylation factors (ARFs); ArfGAPs are a family of proteins containing an ArfGAP catalytic domain that induces the hydrolysis of GTP bound to the small guanine nucleotide-binding protein Arf, a member of the Ras superfamily of GTPases. Like all GTP-binding proteins, Arf proteins function as molecular switches, cycling between GTP (active-membrane bound) and GDP (inactive-cytosolic) form. Conversion to the GTP-bound form requires a guanine nucleotide exchange factor (GEF), whereas conversion to the GDP-bound form is catalyzed by a GTPase activating protein (GAP). In that sense, ArfGAPs were originally proposed to function as terminators of Arf signaling, which is mediated by regulating Arf family GTP-binding proteins. However, recent studies suggest that ArfGAPs can also function as Arf effectors, independently of their GAP enzymatic activity to transduce signals in cells. The ArfGAP domain contains a C4-type zinc finger motif and a conserved arginine that is required for activity, within a specific spacing (CX2CX16CX2CX4R). ArfGAPs, which have multiple functional domains, regulate the membrane trafficking and actin cytoskeleton remodeling via specific interactions with signaling lipids such as phosphoinositides and trafficking proteins, which consequently affect cellular events such as cell growth, migration, and cancer invasion. The ArfGAP family, which includes 31 human ArfGAP-domain containing proteins, is divided into 10 subfamilies based on domain structure and sequence similarity. The ArfGAP nomenclature is mainly based on the protein domain structure. For example, ASAP1 contains ArfGAP, SH3, ANK repeat and PH domains; ARAPs contain ArfGAP, Rho GAP, ANK repeat and PH domains; ACAPs contain ArfGAP, BAR (coiled coil), ANK repeat and PH domains; and AGAPs contain Arf GAP, GTP-binding protein-like, ANK repeat and PH domains. Furthermore, the ArfGAPs can be classified into two major types of subfamilies, according to the overall domain structure: the ArfGAP1 type includes 6 subfamilies (ArfGAP1, ArfGAP2/3, ADAP, SMAP, AGFG, and GIT), which contain the ArfGAP domain at the N-terminus of the protein; and the AZAP type includes 4 subfamilies (ASAP, ACAP, AGAP, and ARAP), which contain an ArfGAP domain between the PH and ANK repeat domains.

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gi 281360495   1 MATFTQDEIDFLRSHGNELCAKTWLGLWDPKRAVH-----QQEQRELMMDKYERKRYY 53
Cdd:cd08838   55 MSTFTPEEVEFLQAGGNEVARKIWLAKWDPRTDPEpdsgdDQKIREFIRLKYVDKRWY 112

ArfGAP domain of the AGFG subfamily (ArfGAP domain and FG repeat-containing proteins); The ArfGAP domain and FG repeat-containing proteins (AFGF) subfamily of Arf GTPase-activating proteins consists of the two structurally-related members: AGFG1 and AGFG2. AGFG1 (alias: HIV-1 Rev binding protein, HRB; Rev interacting protein, RIP; Rev/Rex activating domain-binding protein, RAB) and AGFG2 are involved in the maintenance and spread of immunodeficiency virus type 1 (HIV-1) infection. The ArfGAP domain of AGFG is related to nucleoporins, which is a class of proteins that mediate nucleocytoplasmic transport. AGFG plays a role in the Rev export pathway, which mediates the nucleocytoplasmic transfer of proteins and RNAs, possibly together by the nuclear export receptor CRM1. In humans, the presence of the FG repeat motifs (11 in AGFG1 and 7 in AGFG2) are thought to be required for these proteins to act as HIV-1 Rev cofactors. Hence, AGFG promotes movement of Rev-responsive element-containing RNAs from the nuclear periphery to the cytoplasm, which is an essential step for HIV-1 replication.

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                 ....*....|....*....|....*....|....*....|....*....|....*...
gi 281360495   1 MATFTQDEIDFLRSHGNELCAKTWLGLWDPKRAVH-----QQEQRELMMDKYERKRYY 53
Cdd:cd08838   55 MSTFTPEEVEFLQAGGNEVARKIWLAKWDPRTDPEpdsgdDQKIREFIRLKYVDKRWY 112

ArfGAP domain of the AGFG subfamily (ArfGAP domain and FG repeat-containing proteins); The ArfGAP domain and FG repeat-containing proteins (AFGF) subfamily of Arf GTPase-activating proteins consists of the two structurally-related members: AGFG1 and AGFG2. AGFG1 (alias: HIV-1 Rev binding protein, HRB; Rev interacting protein, RIP; Rev/Rex activating domain-binding protein, RAB) and AGFG2 are involved in the maintenance and spread of immunodeficiency virus type 1 (HIV-1) infection. The ArfGAP domain of AGFG is related to nucleoporins, which is a class of proteins that mediate nucleocytoplasmic transport. AGFG plays a role in the Rev export pathway, which mediates the nucleocytoplasmic transfer of proteins and RNAs, possibly together by the nuclear export receptor CRM1. In humans, the presence of the FG repeat motifs (11 in AGFG1 and 7 in AGFG2) are thought to be required for these proteins to act as HIV-1 Rev cofactors. Hence, AGFG promotes movement of Rev-responsive element-containing RNAs from the nuclear periphery to the cytoplasm, which is an essential step for HIV-1 replication.

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                 ....*....|....*....|....*....|....*....|....*....|....*...
gi 281360495   1 MATFTQDEIDFLRSHGNELCAKTWLGLWDPKRAVH-----QQEQRELMMDKYERKRYY 53
Cdd:cd08838   55 MSTFTPEEVEFLQAGGNEVARKIWLAKWDPRTDPEpdsgdDQKIREFIRLKYVDKRWY 112

ArfGAP domain of AGFG2 (ArfGAP domain and FG repeat-containing protein 2); The ArfGAP domain and FG repeat-containing proteins (AFGF) subfamily of Arf GTPase-activating proteins consists of the two structurally-related members: AGFG1 and AGFG2. AGFG2 is a member of the HIV-1 Rev binding protein (HRB) family and contains one Arf-GAP zinc finger domain, several Phe-Gly (FG) motifs, and four Asn-Pro-Phe (NPF) motifs. AGFG2 interacts with Eps15 homology (EH) domains and plays a role in the Rev export pathway, which mediates the nucleocytoplasmic transfer of proteins and RNAs. In humans, the presence of the FG repeat motifs (11 in AGFG1 and 7 in AGFG2) are thought to be required for these proteins to act as HIV-1 Rev cofactors. Hence, AGFG promotes movement of Rev-responsive element-containing RNAs from the nuclear periphery to the cytoplasm, which is an essential step for HIV-1 replication.

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                 ....*....|....*....|....*....|....*....|....*....|....*....
gi 281360495   1 MATFTQDEIDFLRSHGNELCAKTWLGLWDPKRAV-----HQQEQRELMMDKYERKRYYL 54
Cdd:cd17903   58 MTTFTEPEVLFLQARGNEVCRKIWLGLFDARTSLipdsrDPQKVKEFLQEKYEKKRWYV 116