Syntaxin; Syntaxins are the prototype family of SNARE proteins. They usually consist of three main regions - a C-terminal transmembrane region, a central SNARE domain which is characteriztic of and conserved in all syntaxins (pfam05739), and an N-terminal domain that is featured in this entry. This domain varies between syntaxin isoforms; in syntaxin 1A it is found as three alpha-helices with a left-handed twist. It may fold back on the SNARE domain to allow the molecule to adopt a 'closed' configuration that prevents formation of the core fusion complex - it thus has an auto-inhibitory role. The function of syntaxins is determined by their localization. They are involved in neuronal exocytosis, ER-Golgi transport and Golgi-endosome transport, for example. They also interact with other proteins as well as those involved in SNARE complexes. These include vesicle coat proteins, Rab GTPases, and tethering factors.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424  45 FLEEAEKVKTEMGSIREILLKLQQANEETKSAHKPETLKSLRNTINIDIVTVLKKARSIRSHLEEMDRANAAKKRLSGSK 124
Cdd:pfam00804   2 FFKEVQEIKEEIEKIRLLVKKLQKQNEESKLLTSARRMSVIKRRMNSIARDIKKRAESIKRRLEALDKSNAENEKKPGCG 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424 125 EGTAIYRTRIAVTNGLRKKLKELMMEFQSLRQRMMTEYKETVGRRYFTVTGEKANEEVIEKIISDGVEEFLGRVIKEHGQ 204
Cdd:pfam00804  82 PGSAVDRIRRSQTAALRKKLKEVMAEYNELRERIREEYKEVIQRQYETVTGKEVSEEEIEEMIETGSESVFQKAILEQGR 161

                         170       180       190       200
                  ....*....|....*....|....*....|....*....|....*
gi 1280989424 205 GgkvVVAETVEEIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQG 249
Cdd:pfam00804 162 G---QARSALSEIEERHKELKELESSLKELHQIFLDMAVLVEAQG 203

Syntaxin; Syntaxins are the prototype family of SNARE proteins. They usually consist of three main regions - a C-terminal transmembrane region, a central SNARE domain which is characteriztic of and conserved in all syntaxins (pfam05739), and an N-terminal domain that is featured in this entry. This domain varies between syntaxin isoforms; in syntaxin 1A it is found as three alpha-helices with a left-handed twist. It may fold back on the SNARE domain to allow the molecule to adopt a 'closed' configuration that prevents formation of the core fusion complex - it thus has an auto-inhibitory role. The function of syntaxins is determined by their localization. They are involved in neuronal exocytosis, ER-Golgi transport and Golgi-endosome transport, for example. They also interact with other proteins as well as those involved in SNARE complexes. These include vesicle coat proteins, Rab GTPases, and tethering factors.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424  45 FLEEAEKVKTEMGSIREILLKLQQANEETKSAHKPETLKSLRNTINIDIVTVLKKARSIRSHLEEMDRANAAKKRLSGSK 124
Cdd:pfam00804   2 FFKEVQEIKEEIEKIRLLVKKLQKQNEESKLLTSARRMSVIKRRMNSIARDIKKRAESIKRRLEALDKSNAENEKKPGCG 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424 125 EGTAIYRTRIAVTNGLRKKLKELMMEFQSLRQRMMTEYKETVGRRYFTVTGEKANEEVIEKIISDGVEEFLGRVIKEHGQ 204
Cdd:pfam00804  82 PGSAVDRIRRSQTAALRKKLKEVMAEYNELRERIREEYKEVIQRQYETVTGKEVSEEEIEEMIETGSESVFQKAILEQGR 161

                         170       180       190       200
                  ....*....|....*....|....*....|....*....|....*
gi 1280989424 205 GgkvVVAETVEEIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQG 249
Cdd:pfam00804 162 G---QARSALSEIEERHKELKELESSLKELHQIFLDMAVLVEAQG 203

Syntaxin N-terminal domain; Three-helix domain that (in Sso1p) slows the rate of its reaction with the SNAP-25 homologue Sec9p

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424   40 GDMGLFLEEAEKVKTEMGSIREILLKLQQANEETKSAHKPEtlKSLRNTINIDIVTVLKKARSIRSHLEEMDRANAAKkr 119
Cdd:smart00503   1 SNLDEFFEKVEEIRANIQKISQNVAELQKLHEELLTPPDAD--KELREKLERLIDDIKRLAKEIRAKLKELEKENLEN-- 76

                           90       100       110       120
                   ....*....|....*....|....*....|....*....|....
gi 1280989424  120 lsgSKEGTAIYRTRIAVTNGLRKKLKELMMEFQSLRQRMMTEYK 163
Cdd:smart00503  77 ---RASGSASDRTRKAQTEKLRKKFKEVMNEFQRLQRKYREREK 117

SNARE motif of syntaxin 12; Syntaxin 12 (STX12, also known as STX13 and STX14) forms a complex with SNAP25 (Qb/Qc) or SNAP29 (Qb/Qc) and VAMP2 or VAMP3 (R-SNARE) and plays a role in plasma membrane to early endosome transport. Syntaxin 12 is a member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) which mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1280989424 217 IQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKSAKELQRSS 283
Cdd:cd15876     1 IKERETAIQQLEADILDVNQIFKDLAMMIHDQGDMIDSIEANVESAEVHVERASEQLQRAAYYQKKS 67

SNARE domain; Most if not all vesicular membrane fusion events in eukaryotic cells are believed to be mediated by a conserved fusion machinery, the SNARE [soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors] machinery. The SNARE domain is thought to act as a protein-protein interaction module in the assembly of a SNARE protein complex.

                          10        20        30
                  ....*....|....*....|....*....|....*....
gi 1280989424 250 EKMDNIEHHVMNASQYVRDGTKELKSAKELQRSSRKCMC 288
Cdd:pfam05739   1 EMLDRIDTNVENAQSNVERAQKELKKAVKYQKSNRKLKC 39

Syntaxin; Syntaxins are the prototype family of SNARE proteins. They usually consist of three main regions - a C-terminal transmembrane region, a central SNARE domain which is characteriztic of and conserved in all syntaxins (pfam05739), and an N-terminal domain that is featured in this entry. This domain varies between syntaxin isoforms; in syntaxin 1A it is found as three alpha-helices with a left-handed twist. It may fold back on the SNARE domain to allow the molecule to adopt a 'closed' configuration that prevents formation of the core fusion complex - it thus has an auto-inhibitory role. The function of syntaxins is determined by their localization. They are involved in neuronal exocytosis, ER-Golgi transport and Golgi-endosome transport, for example. They also interact with other proteins as well as those involved in SNARE complexes. These include vesicle coat proteins, Rab GTPases, and tethering factors.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424  45 FLEEAEKVKTEMGSIREILLKLQQANEETKSAHKPETLKSLRNTINIDIVTVLKKARSIRSHLEEMDRANAAKKRLSGSK 124
Cdd:pfam00804   2 FFKEVQEIKEEIEKIRLLVKKLQKQNEESKLLTSARRMSVIKRRMNSIARDIKKRAESIKRRLEALDKSNAENEKKPGCG 81

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424 125 EGTAIYRTRIAVTNGLRKKLKELMMEFQSLRQRMMTEYKETVGRRYFTVTGEKANEEVIEKIISDGVEEFLGRVIKEHGQ 204
Cdd:pfam00804  82 PGSAVDRIRRSQTAALRKKLKEVMAEYNELRERIREEYKEVIQRQYETVTGKEVSEEEIEEMIETGSESVFQKAILEQGR 161

                         170       180       190       200
                  ....*....|....*....|....*....|....*....|....*
gi 1280989424 205 GgkvVVAETVEEIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQG 249
Cdd:pfam00804 162 G---QARSALSEIEERHKELKELESSLKELHQIFLDMAVLVEAQG 203

Syntaxin N-terminal domain; Three-helix domain that (in Sso1p) slows the rate of its reaction with the SNAP-25 homologue Sec9p

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424   40 GDMGLFLEEAEKVKTEMGSIREILLKLQQANEETKSAHKPEtlKSLRNTINIDIVTVLKKARSIRSHLEEMDRANAAKkr 119
Cdd:smart00503   1 SNLDEFFEKVEEIRANIQKISQNVAELQKLHEELLTPPDAD--KELREKLERLIDDIKRLAKEIRAKLKELEKENLEN-- 76

                           90       100       110       120
                   ....*....|....*....|....*....|....*....|....
gi 1280989424  120 lsgSKEGTAIYRTRIAVTNGLRKKLKELMMEFQSLRQRMMTEYK 163
Cdd:smart00503  77 ---RASGSASDRTRKAQTEKLRKKFKEVMNEFQRLQRKYREREK 117

SNARE motif, subgroup Qa; SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins consist of coiled-coil helices (called SNARE motifs) which mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complex mediates membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle. Their SNARE motifs form twisted and parallel heterotetrameric helix bundles. Examples for members of the Qa SNAREs are syntaxin 18, syntaxin 5, syntaxin 16, and syntaxin 1.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 1280989424 217 IQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKS 275
Cdd:cd15840     1 IEEREEEIREIESSIGEVNEIFKDLATLVTEQGEQIDNIENNIEEAAANTEEANKELRK 59

SNARE motif of syntaxin 2; Syntaxin 2 (STX2), also known as epimorphin (EPM or EPIM), may interact with SNAP-23 (Qb/c) and genetic varioations are associated with type 1 von Willebrand disease (VWD). Syntaxin 2 is a member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1280989424 216 EIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKSAKELQ 280
Cdd:cd15882     4 EIESRHKDIMKLESSIRELHDMFVDMAMLVETQGEMINNIEKNVHNAVEYVEHAKEETKKAVKYQ 68

t-SNARE complex subunit, syntaxin [Intracellular trafficking, secretion, and vesicular transport];

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424 132 TRIAVTNGLRKKLKELMMEFQSLRQRMMTEYKETVgRRYFTVTGEKANEEVIEKIISD--GVEEFLGRVIKEHGQGGkvv 209
Cdd:COG5074    97 NKQAQAENVRQKFLKLIQDYRIIDSNYREEEKEQA-RRQYIIAQPEATEDEVEAAINDvnGQQVFSQALLNANRRGE--- 172

                          90       100       110       120       130       140       150
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1280989424 210 vAETV-EEIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKSAKELQRSSRK 285
Cdd:COG5074   173 -AKTAlAEVQARHQEIKKIEKTMAELTQLFNDMEELVIEQQENVDVIDKNVEDAQENVEQGVGHTDKAVKSARAARK 248

SNARE motif of syntaxin 3; Syntaxin 3 (STX3) has been shown to form a complex with VAMP8 (R-SNARE) and SNAP-23 (Qb/c) in mast cells. Mutations have been implicated in human microvillus inclusion disease (MVID), a disorder of the differentiation of intestinal epithelium. Syntaxin 3 is a member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1280989424 214 VEEIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKSAKELQR 281
Cdd:cd15881     2 LSEIEGRHKDIVRLESSIKELHDMFVDIAMLVENQGEMLDNIELNVMKTVDHVEKARDETKKAVKYQS 69

SNARE motif of syntaxin 12; Syntaxin 12 (STX12, also known as STX13 and STX14) forms a complex with SNAP25 (Qb/Qc) or SNAP29 (Qb/Qc) and VAMP2 or VAMP3 (R-SNARE) and plays a role in plasma membrane to early endosome transport. Syntaxin 12 is a member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) which mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1280989424 217 IQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKSAKELQRSS 283
Cdd:cd15876     1 IKERETAIQQLEADILDVNQIFKDLAMMIHDQGDMIDSIEANVESAEVHVERASEQLQRAAYYQKKS 67

SNARE motif of syntaxin 4; Syntaxin-4 forms a complex with SNAP-23 (Qb/Qc) and R-SNAREs VAMP8, VAMP2 and VAMP7 which plays a role in exocytosis of secetory granule. Syntaxin 4 is member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|
gi 1280989424 216 EIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKS 275
Cdd:cd15883     4 EIEARHSEIQKLERSIRELHDMFTYLAMEVEAQGEMIDRIEKNILSSADYVEKAQEHVKT 63

SNARE motif of syntaxin 16; Syntaxin 16 is located in trans-Golgi network (TGN) and regulated by the SM protein Vps45p. It forms a complex with syntaxin 6 (Qc), Vti1a (Qb) and VAMP4 (R-SNARE) and is involved in the regulation of recycling of early endosomes to the trans-Golgi network (TGN). Syntaxin 16 is a member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*...
gi 1280989424 217 IQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELK 274
Cdd:cd15845     1 IQERDREIAKIVESINELAEIFKDLATLVIEQGTILDRIDYNIEQTATRVEKGVKELK 58

SNARE domain; Most if not all vesicular membrane fusion events in eukaryotic cells are believed to be mediated by a conserved fusion machinery, the SNARE [soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors] machinery. The SNARE domain is thought to act as a protein-protein interaction module in the assembly of a SNARE protein complex.

                          10        20        30
                  ....*....|....*....|....*....|....*....
gi 1280989424 250 EKMDNIEHHVMNASQYVRDGTKELKSAKELQRSSRKCMC 288
Cdd:pfam05739   1 EMLDRIDTNVENAQSNVERAQKELKKAVKYQKSNRKLKC 39

SNARE motif of syntaxin 19; Syntaxin 19 has been shown to have the potential to form SNARE complexes with SNAP-23, 25 and 29 (Qb/Qc) and VAMP3 and VAMP8 (R-SNARE), indicating a role in post-Golgi trafficking or plasma membrane fusion. Syntaxin 19 is member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 1280989424 216 EIQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELK 274
Cdd:cd15879     4 EIEQRHKELVSLENQIKDLKDLFIQISLLVEEQGEMINNIEISVNNTQEYVQASKEKFG 62

SNARE motif of syntaxin 5; Syntaxin 5 (Syn5) regulates the transport from the ER to the Golgi, as well as the early/recycling endosomes to the trans-Golgi network and participates in the assembly of transitional ER and the Golgi, lipid droplet fusion, and cytokinesis. Syn5 exists in 2 isoforms, long (42 kDa) and short (35 kDa). The short form is localized in the Golgi complex, whereas the long form is additionally found in the endoplasmic reticulum (ER). The syntaxin-5 SNARE complexes, which also contain Bet1 (Qc) and either GS27 (Qb) and Sec22B (R-SNARE) or GS28 (Qb) and Ykt6 (R-SNARE), regulate the early secretory pathway of eukaryotic cells at the level of endoplasmic reticulum (ER) to Golgi transport. The syntaxin-5 SNARE complex, which also contains GS15 (Qc), GS28 (Qb) and Ykt6 (R-SNAREs) is involved in the transport from the trans-Golgi network to the cis-Golgi. Syn5 is member of the Qa subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain. The SNARE complex mediates membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic center layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1280989424 217 IQDRHGAAKEIEKSLLELHQVFLDMAVMVEAQGEKMDNIEHHVMNASQYVRDGTKELKSAKELQRSSRKCM 287
Cdd:cd15844     1 LQSRADAVQNIESTIVELGQIFQQLATMVAEQGEMVQRIDENVEDALANVEAAHSELLKYYRSISSNRWLI 71