Ras-related in brain (Rab) family of small guanosine triphosphatases (GTPases); Rab GTPases form the largest family within the Ras superfamily. There are at least 60 Rab genes in the human genome, and a number of Rab GTPases are conserved from yeast to humans. Rab GTPases are small, monomeric proteins that function as molecular switches to regulate vesicle trafficking pathways. The different Rab GTPases are localized to the cytosolic face of specific intracellular membranes, where they regulate distinct steps in membrane traffic pathways. In the GTP-bound form, Rab GTPases recruit specific sets of effector proteins onto membranes. Through their effectors, Rab GTPases regulate vesicle formation, actin- and tubulin-dependent vesicle movement, and membrane fusion. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which mask C-terminal lipid binding and promote cytosolic localization. While most unicellular organisms possess 5-20 Rab members, several have been found to possess 60 or more Rabs; for many of these Rab isoforms, homologous proteins are not found in other organisms. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins. Since crystal structures often lack C-terminal residues, the lipid modification site is not available for annotation in many of the CDs in the hierarchy, but is included where possible.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   5 KILFVGPCESGKTVLANFLTESSDITEYSPTQGVrilEFENPHVTSNNKgtGCEFELWDCGGDAKFESCWPALMKDAHGV 84
Cdd:cd00154   2 KIVLIGDSGVGKTSLLLRFVDNKFSENYKSTIGV---DFKSKTIEVDGK--KVKLQIWDTAGQERFRSITSSYYRGAHGA 76

                        90       100       110
                ....*....|....*....|....*....|....*....
gi 74733725  85 VIVFnaDIPSHR--KEMEMWYScFVQQPSLQDTQCMLIA 121
Cdd:cd00154  77 ILVY--DVTNREsfENLDKWLN-ELKEYAPPNIPIILVG 112

Rab subfamily of small GTPases; Rab GTPases are implicated in vesicle trafficking.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725      5 KILFVGPCESGKTVLANFLTESSDITEYSPTQGV----RILEFEnphvtsnnkGTGCEFELWDCGGDAKFESCWPALMKD 80
Cdd:smart00175   2 KIILIGDSGVGKSSLLSRFTDGKFSEQYKSTIGVdfktKTIEVD---------GKRVKLQIWDTAGQERFRSITSSYYRG 72

                           90       100       110       120
                   ....*....|....*....|....*....|....*....|....
gi 74733725     81 AHGVVIVFnaDIPSHR--KEMEMWYSCFVQQpSLQDTQCMLIAH 122
Cdd:smart00175  73 AVGALLVY--DITNREsfENLENWLKELREY-ASPNVVIMLVGN 113

Ras-related in brain (Rab) family of small guanosine triphosphatases (GTPases); Rab GTPases form the largest family within the Ras superfamily. There are at least 60 Rab genes in the human genome, and a number of Rab GTPases are conserved from yeast to humans. Rab GTPases are small, monomeric proteins that function as molecular switches to regulate vesicle trafficking pathways. The different Rab GTPases are localized to the cytosolic face of specific intracellular membranes, where they regulate distinct steps in membrane traffic pathways. In the GTP-bound form, Rab GTPases recruit specific sets of effector proteins onto membranes. Through their effectors, Rab GTPases regulate vesicle formation, actin- and tubulin-dependent vesicle movement, and membrane fusion. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which mask C-terminal lipid binding and promote cytosolic localization. While most unicellular organisms possess 5-20 Rab members, several have been found to possess 60 or more Rabs; for many of these Rab isoforms, homologous proteins are not found in other organisms. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins. Since crystal structures often lack C-terminal residues, the lipid modification site is not available for annotation in many of the CDs in the hierarchy, but is included where possible.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   5 KILFVGPCESGKTVLANFLTESSDITEYSPTQGVrilEFENPHVTSNNKgtGCEFELWDCGGDAKFESCWPALMKDAHGV 84
Cdd:cd00154   2 KIVLIGDSGVGKTSLLLRFVDNKFSENYKSTIGV---DFKSKTIEVDGK--KVKLQIWDTAGQERFRSITSSYYRGAHGA 76

                        90       100       110
                ....*....|....*....|....*....|....*....
gi 74733725  85 VIVFnaDIPSHR--KEMEMWYScFVQQPSLQDTQCMLIA 121
Cdd:cd00154  77 ILVY--DVTNREsfENLDKWLN-ELKEYAPPNIPIILVG 112

Ras family; Includes sub-families Ras, Rab, Rac, Ral, Ran, Rap Ypt1 and more. Shares P-loop motif with GTP_EFTU, arf and myosin_head. See pfam00009 pfam00025, pfam00063. As regards Rab GTPases, these are important regulators of vesicle formation, motility and fusion. They share a fold in common with all Ras GTPases: this is a six-stranded beta-sheet surrounded by five alpha-helices.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725     5 KILFVGPCESGKTVLANFLTESSDITEYSPTQGVrilEFENPHVTSNNKGtgCEFELWDCGGDAKFESCWPALMKDAHGV 84
Cdd:pfam00071   1 KLVLVGDGGVGKSSLLIRFTQNKFPEEYIPTIGV---DFYTKTIEVDGKT--VKLQIWDTAGQERFRALRPLYYRGADGF 75

                          90       100
                  ....*....|....*....|..
gi 74733725    85 VIVFnaDIPSHR--KEMEMWYS 104
Cdd:pfam00071  76 LLVY--DITSRDsfENVKKWVE 95

Rnd3/RhoE/Rho8 GTPases; Rnd3/RhoE/Rho8 subfamily. Rnd3/RhoE/Rho8 is a member of the novel Rho subfamily Rnd, together with Rnd1/Rho6 and Rnd2/Rho7. Rnd3/RhoE is known to bind the serine-threonine kinase ROCK I. Unphosphorylated Rnd3/RhoE associates primarily with membranes, but ROCK I-phosphorylated Rnd3/RhoE localizes in the cytosol. Phosphorylation of Rnd3/RhoE correlates with its activity in disrupting RhoA-induced stress fibers and inhibiting Ras-induced fibroblast transformation. In cells that lack stress fibers, such as macrophages and monocytes, Rnd3/RhoE induces a redistribution of actin, causing morphological changes in the cell. In addition, Rnd3/RhoE has been shown to inhibit cell cycle progression in G1 phase at a point upstream of the pRb family pocket protein checkpoint. Rnd3/RhoE has also been shown to inhibit Ras- and Raf-induced fibroblast transformation. In mammary epithelial tumor cells, Rnd3/RhoE regulates the assembly of the apical junction complex and tight junction formation. Rnd3/RhoE is underexpressed in prostate cancer cells both in vitro and in vivo; re-expression of Rnd3/RhoE suppresses cell cycle progression and increases apoptosis, suggesting it may play a role in tumor suppression. Most Rho proteins contain a lipid modification site at the C-terminus, with a typical sequence motif CaaX, where a = an aliphatic amino acid and X = any amino acid. Lipid binding is essential for membrane attachment, a key feature of most Rho proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   2 LKAKILFVGPCESGKTVLANFLTESSDITEYSPTQgvrileFENPHVTSNNKGTGCEFELWDCGGDAKFESCWPALMKDA 81
Cdd:cd04172   4 VKCKIVVVGDSQCGKTALLHVFAKDCFPENYVPTV------FENYTASFEIDTQRIELSLWDTSGSPYYDNVRPLSYPDS 77

                        90
                ....*....|..
gi 74733725  82 HGVVIVFNADIP 93
Cdd:cd04172  78 DAVLICFDISRP 89

Rat sarcoma (Ras)-like superfamily of small guanosine triphosphatases (GTPases); Ras-like GTPase superfamily. The Ras-like superfamily of small GTPases consists of several families with an extremely high degree of structural and functional similarity. The Ras superfamily is divided into at least four families in eukaryotes: the Ras, Rho, Rab, and Sar1/Arf families. This superfamily also includes proteins like the GTP translation factors, Era-like GTPases, and G-alpha chain of the heterotrimeric G proteins. Members of the Ras superfamily regulate a wide variety of cellular functions: the Ras family regulates gene expression, the Rho family regulates cytoskeletal reorganization and gene expression, the Rab and Sar1/Arf families regulate vesicle trafficking, and the Ran family regulates nucleocytoplasmic transport and microtubule organization. The GTP translation factor family regulates initiation, elongation, termination, and release in translation, and the Era-like GTPase family regulates cell division, sporulation, and DNA replication. Members of the Ras superfamily are identified by the GTP binding site, which is made up of five characteristic sequence motifs, and the switch I and switch II regions.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   7 LFVGPCESGKTVLANFLTESS---DITEYSPTQGVRILEFENPHVtsnnkgtGCEFELWDCGG-----DAKFESCWPALM 78
Cdd:cd00882   1 VVVGRGGVGKSSLLNALLGGEvgeVSDVPGTTRDPDVYVKELDKG-------KVKLVLVDTPGldefgGLGREELARLLL 73

                        90       100
                ....*....|....*....|....*
gi 74733725  79 KDAHGVVIVFNADIPSHRKEMEMWY 103
Cdd:cd00882  74 RGADLILLVVDSTDRESEEDAKLLI 98

small GTP-binding protein domain; Proteins with a small GTP-binding domain recognized by this model include Ras, RhoA, Rab11, translation elongation factor G, translation initiation factor IF-2, tetratcycline resistance protein TetM, CDC42, Era, ADP-ribosylation factors, tdhF, and many others. In some proteins the domain occurs more than once.This model recognizes a large number of small GTP-binding proteins and related domains in larger proteins. Note that the alpha chains of heterotrimeric G proteins are larger proteins in which the NKXD motif is separated from the GxxxxGK[ST] motif (P-loop) by a long insert and are not easily detected by this model. [Unknown function, General]

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725     4 AKILFVGPCESGKTVLAN-FLTESSDITEYSPTQGvriLEFENPHVTSNnkGTGCEFELWDCGGDAKFESCWPALMKDAH 82
Cdd:TIGR00231   2 IKIVIVGHPNVGKSTLLNsLLGNKGSITEYYPGTT---RNYVTTVIEED--GKTYKFNLLDTAGQEDYDAIRRLYYPQVE 76

                          90
                  ....*....|.
gi 74733725    83 GVVIVFNADIP 93
Cdd:TIGR00231  77 RSLRVFDIVIL 87

Ras of complex proteins (Roc) C-terminal of Roc (COR) domain family; RocCOR (or Roco) protein family is characterized by a superdomain containing a Ras-like GTPase domain, called Roc (Ras of complex proteins), and a characteristic second domain called COR (C-terminal of Roc). A kinase domain and diverse regulatory domains are also often found in Roco proteins. Their functions are diverse; in Dictyostelium discoideum, which encodes 11 Roco proteins, they are involved in cell division, chemotaxis and development, while in human, where 4 Roco proteins (LRRK1, LRRK2, DAPK1, and MFHAS1) are encoded, these proteins are involved in epilepsy and cancer. Mutations in LRRK2 (leucine-rich repeat kinase 2) are known to cause familial Parkinson's disease.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   3 KAKILFVGPCESGKTVLANFLTESSDITEYSPTQGVRILEFENPhvtsNNKGTGCEFELWDCGGDAKFESCWPALMKDAH 82
Cdd:cd09914   1 EAKLMLVGQGGVGKTSLCKQLIGEKFDGDESSTHGINVQDWKIP----APERKKIRLNVWDFGGQEIYHATHQFFLTSRS 76

                        90       100
                ....*....|....*....|
gi 74733725  83 GVVIVFNADIPSHRKEMEMW 102
Cdd:cd09914  77 LYLLVFDLRTGDEVSRVPYW 96

Ras homology family 4 (Rho4) of small guanosine triphosphatases (GTPases)-like; Rho4 is a GTPase that controls septum degradation by regulating secretion of Eng1 or Agn1 during cytokinesis. Rho4 also plays a role in cell morphogenesis. Rho4 regulates septation and cell morphology by controlling the actin cytoskeleton and cytoplasmic microtubules. The localization of Rho4 is modulated by Rdi1, which may function as a GDI, and by Rga9, which is believed to function as a GAP. In S. pombe, both Rho4 deletion and Rho4 overexpression result in a defective cell wall, suggesting a role for Rho4 in maintaining cell wall integrity. Most Rho proteins contain a lipid modification site at the C-terminus, with a typical sequence motif CaaX, where a = an aliphatic amino acid and X = any amino acid. Lipid binding is essential for membrane attachment, a key feature of most Rho proteins.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   2 LKAKILFVGPCESGKTVLANFLTESSDITEYSPTQgvrileFENpHVTSNNKGTGCEFE--LWDCGGDAKFESCWPALMK 79
Cdd:cd04132   2 LKVKIVVVGDGGCGKTCLLMVYAQGSFPEEYVPTV------FEN-YVTTLQVPNGKIIElaLWDTAGQEDYDRLRPLSYP 74

                        90       100
                ....*....|....*....|....*
gi 74733725  80 DAHGVVIVFNADIPSHRKEM-EMWY 103
Cdd:cd04132  75 DVDVILICYSVDNPTSLDNVeDKWY 99

Rnd1/Rho6 GTPases; Rnd1/Rho6 is a member of the novel Rho subfamily Rnd, together with Rnd2/Rho7 and Rnd3/RhoE/Rho8. Rnd1/Rho6 binds GTP but does not hydrolyze it to GDP, indicating that it is constitutively active. In rat, Rnd1/Rho6 is highly expressed in the cerebral cortex and hippocampus during synapse formation, and plays a role in spine formation. Rnd1/Rho6 is also expressed in the liver and in endothelial cells, and is upregulated in uterine myometrial cells during pregnancy. Like Rnd3/RhoE/Rho8, Rnd1/Rho6 is believed to function as an antagonist to RhoA. Most Rho proteins contain a lipid modification site at the C-terminus, with a typical sequence motif CaaX, where a = an aliphatic amino acid and X = any amino acid. Lipid binding is essential for membrane attachment, a key feature of most Rho proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   1 MLKAKILFVGPCESGKTVLANFLTESSDITEYSPTQgvrileFENPHVTSNNKGTGCEFELWDCGGDAKFESCWPALMKD 80
Cdd:cd04174  11 VVRCKLVLVGDVQCGKTAMLQVLAKDCYPETYVPTV------FENYTACLETEEQRVELSLWDTSGSPYYDNVRPLCYSD 84

                        90       100
                ....*....|....*....|....*
gi 74733725  81 AHGVVIVFNADIP-SHRKEMEMWYS 104
Cdd:cd04174  85 SDAVLLCFDISRPeIFDSALKKWRA 109

Arl2-like protein 1 (Arl2l1) and Arl13; Arl2l1 (Arl2-like protein 1) and Arl13 form a subfamily of the Arf family of small GTPases. Arl2l1 was identified in human cells during a search for the gene(s) responsible for Bardet-Biedl syndrome (BBS). Like Arl6, the identified BBS gene, Arl2l1 is proposed to have cilia-specific functions. Arl13 is found on the X chromosome, but its expression has not been confirmed; it may be a pseudogene.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   6 ILFVGPCESGKTVLANFLTESSDiTEYSPTQGVRILEFEnphvTSNnkgtgCEFELWDCGGDAKFESCWPALMKDAHGVV 85
Cdd:cd04161   2 LLTVGLDNAGKTTLVSALQGEIP-KKVAPTVGFTPTKLR----LDK-----YEVCIFDLGGGANFRGIWVNYYAEAHGLV 71

                ..
gi 74733725  86 IV 87
Cdd:cd04161  72 FV 73

Signal recognition particle receptor, beta subunit (SR-beta), together with SR-alpha, forms the heterodimeric signal recognition particle (SRP); Signal recognition particle receptor, beta subunit (SR-beta). SR-beta and SR-alpha form the heterodimeric signal recognition particle (SRP or SR) receptor that binds SRP to regulate protein translocation across the ER membrane. Nascent polypeptide chains are synthesized with an N-terminal hydrophobic signal sequence that binds SRP54, a component of the SRP. SRP directs targeting of the ribosome-nascent chain complex (RNC) to the ER membrane via interaction with the SR, which is localized to the ER membrane. The RNC is then transferred to the protein-conducting channel, or translocon, which facilitates polypeptide translation across the ER membrane or integration into the ER membrane. SR-beta is found only in eukaryotes; it is believed to control the release of the signal sequence from SRP54 upon binding of the ribosome to the translocon. High expression of SR-beta has been observed in human colon cancer, suggesting it may play a role in the development of this type of cancer.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   6 ILFVGPCESGKTVLANFLTESsditEYSPTQgVRILEFENPHVTSNNKGTGceFELWDCGGDAKF-ESCWPALMKDAHGV 84
Cdd:cd04105   3 VLLLGPSDSGKTALFTKLTTG----KVRSTV-TSIEPNVASFYSNSSKGKK--LTLVDVPGHEKLrDKLLEYLKASLKAI 75

                        90       100       110       120       130       140       150       160
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725  85 VIVFN--ADIPSHRKEMEMWYSCFVQQPSLQDTQCMLIAHHKpgsgDDkgsLSLSPPLNKLKLVhsnLEDDPEEIRMEFI 162
Cdd:cd04105  76 VFVVDsaTFQKNIRDVAEFLYDILTDLEKIKNKIPILIACNK----QD---LFTAKPAKKIKEL---LEKEINTLRESRS 145

                ....*....
gi 74733725 163 KYLKSIINS 171
Cdd:cd04105 146 KSLESLDGD 154

Rab GTPase family 39 (Rab39); Found in eukaryotes, Rab39 is mainly found in epithelial cell lines, but is distributed widely in various human tissues and cell lines. It is believed to be a novel Rab protein involved in regulating Golgi-associated vesicular transport during cellular endocytosis. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which facilitate Rab recycling by masking C-terminal lipid binding and promoting cytosolic localization. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   5 KILFVGPCESGKTVLANFLTES--SDITEysPTQGV----RILEFEnphvtsnnKGTGCEFELWDCGGDAKFESCWPALM 78
Cdd:cd04111   4 RLIVIGDSTVGKSSLLKRFTEGrfAEVSD--PTVGVdffsRLIEIE--------PGVRIKLQLWDTAGQERFRSITRSYY 73

                        90       100
                ....*....|....*....|....*..
gi 74733725  79 KDAHGVVIVFnaDIPSHR--KEMEMWY 103
Cdd:cd04111  74 RNSVGVLLVF--DITNREsfEHVHDWL 98

Arf-like 6 (Arl6) GTPase; Arl6 (Arf-like 6) forms a subfamily of the Arf family of small GTPases. Arl6 expression is limited to the brain and kidney in adult mice, but it is expressed in the neural plate and somites during embryogenesis, suggesting a possible role for Arl6 in early development. Arl6 is also believed to have a role in cilia or flagella function. Several proteins have been identified that bind Arl6, including Arl6 interacting protein (Arl6ip), and SEC61beta, a subunit of the heterotrimeric conducting channel SEC61p. Based on Arl6 binding to these effectors, Arl6 is also proposed to play a role in protein transport, membrane trafficking, or cell signaling during hematopoietic maturation. At least three specific homozygous Arl6 mutations in humans have been found to cause Bardet-Biedl syndrome, a disorder characterized by obesity, retinopathy, polydactyly, renal and cardiac malformations, learning disabilities, and hypogenitalism. Older literature suggests that Arl6 is a part of the Arl4/Arl7 subfamily, but analyses based on more recent sequence data place Arl6 in its own subfamily.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   6 ILFVGPCESGKTVLANFLTESSDITEY-SPTQGVRILEFEnphvTSNNKgtgceFELWDCGGDAKFESCWPALMKDAHGV 84
Cdd:cd04157   2 ILVLGLDNSGKTTIINQLKPSNAQSQNiVPTVGFNVESFK----KGNLS-----FTAFDMSGQGKYRGLWEHYYKNIQGI 72

                ...
gi 74733725  85 VIV 87
Cdd:cd04157  73 IFV 75

Rab GTPase family 27a (Rab27a); The Rab27a subfamily consists of Rab27a and its highly homologous isoform, Rab27b. Unlike most Rab proteins whose functions remain poorly defined, Rab27a has many known functions. Rab27a has multiple effector proteins, and depending on which effector it binds, Rab27a has different functions as well as tissue distribution and/or cellular localization. Putative functions have been assigned to Rab27a when associated with the effector proteins Slp1, Slp2, Slp3, Slp4, Slp5, DmSlp, rabphilin, Dm/Ce-rabphilin, Slac2-a, Slac2-b, Slac2-c, Noc2, JFC1, and Munc13-4. Rab27a has been associated with several human diseases, including hemophagocytic syndrome (Griscelli syndrome or GS), Hermansky-Pudlak syndrome, and choroidermia. In the case of GS, a rare, autosomal recessive disease, a Rab27a mutation is directly responsible for the disorder. When Rab27a is localized to the secretory granules of pancreatic beta cells, it is believed to mediate glucose-stimulated insulin secretion, making it a potential target for diabetes therapy. When bound to JFC1 in prostate cells, Rab27a is believed to regulate the exocytosis of prostate- specific markers. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which facilitate Rab recycling by masking C-terminal lipid binding and promoting cytosolic localization. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   5 KILFVGPCESGKTVLANFLTESSDITEYSPTQGVrilEFENPHVTSNNKGTG--------CEFELWDCGGDAKFESCWPA 76
Cdd:cd04127   6 KLLALGDSGVGKTTFLYRYTDNKFNPKFITTVGI---DFREKRVVYNSQGPDgtsgkafrVHLQLWDTAGQERFRSLTTA 82

                        90
                ....*....|...
gi 74733725  77 LMKDAHGVVIVFN 89
Cdd:cd04127  83 FFRDAMGFLLMFD 95

Rab GTPase family 28 (Rab28); Rab28 subfamily. First identified in maize, Rab28 has been shown to be a late embryogenesis-abundant (Lea) protein that is regulated by the plant hormone abcisic acid (ABA). In Arabidopsis, Rab28 is expressed during embryo development and is generally restricted to provascular tissues in mature embryos. Unlike maize Rab28, it is not ABA-inducible. Characterization of the human Rab28 homolog revealed two isoforms, which differ by a 95-base pair insertion, producing an alternative sequence for the 30 amino acids at the C-terminus. The two human isoforms are presumably the result of alternative splicing. Since they differ at the C-terminus but not in the GTP-binding region, they are predicted to be targeted to different cellular locations. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which facilitate Rab recycling by masking C-terminal lipid binding and promoting cytosolic localization. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 74733725   5 KILFVGPCESGKTVLANFLTESSDITEYSPTQGV-----RILEFENPHVTsnnkgtgceFELWDCGGDAKFESCWPALMK 79
Cdd:cd04109   2 KIVVLGDGASGKTSLIRRFAQEGFGKSYKQTIGLdffsrRITLPGSLNVT---------LQVWDIGGQQIGGKMLDKYIY 72

                        90       100
                ....*....|....*....|....*.
gi 74733725  80 DAHGVVIVFNADIPSHRKEMEMWYSC 105
Cdd:cd04109  73 GAQAVCLVYDITNSQSFENLEDWLSV 98