The following text describes a protein:
Function:
Cell surface receptor involved in guidance and targeting of growing nerve axons. Required during Bolwig's organ differentiation for accurate and efficient targeting of photoreceptor neuron axons to their synaptic targets in the brain via the P2 intermediate target neuron. Involved in isoneural self-avoidance during dendrite arborization but not in heteroneural recognition and repulsion during tiling by related neurons of the same class. Involved in regulating axon bifurcation and divergent extension in the developing mushroom body. Essential for axon arborisation in ellipsoid body. Exhibits an extraordinary level of molecular diversity resulting from alternative splicing. Isoforms differing in their ectodomain makeup show a high degree of functional redundancy while isoforms with different transmembrane domains are involved in different neuronal morphogenetic processes and are differentially targeted to dendrites or axons. The vast majority of isoforms exhibit strong isoform-specific homophilic binding. Individual cells express a distinct randomly generated repertoire of isoforms. Cell surfaces bearing identical repertoires of Dscam1 isoforms, such as those from the same cell, trigger recognition and avoidance. A subset of isoforms is expressed in fat body cells and hemocytes, cells that are part of the insect immune response, and these isoforms are secreted into the hemolymph. The secreted form comprising the ectodomain can bind to bacteria, such as Escherichia coli, and may act as an opsonin enhancing their phagocytosis by hemocytes.
Subcellular Localization:
Cell membrane; Single-pass membrane protein. Cell projection, neuron projection. Cell projection, axon. Perikaryon. Cell projection, dendrite. Secreted.
Domain:
The ectodomain consists of 10 Ig-like domains. Ig-like domains 2, 3 and 7 are highly variable in different isoforms due to alternative splicing. Ig-like domains 1-8 are sufficient for homodimerization. Dimerization only occurs when all 3 variable Ig-like domains are identical. Intramolecular interactions between Ig-like domain pairs 1-4, 2-3 and 5-6 cause the ectodomain to adopt an S shape conformation, bringing the variable Ig-like domains 2, 3 and 7 into line to form an interaction surface. During dimerization Ig-like domains 2, 3 and 7 self-interact in a modular fashion with their corresponding domain on the opposite molecule in an antiparallel orientation. The Ig-like domain isoform encoded by exon 9.33 is unable to bind another copy of itself; The cytoplasmic domain is required to convert the recognition and adhesion of Dscam1 molecules on opposing membranes into a repulsion signal, possibly by recruiting components of signaling pathways involved in actin cytoskeleton regulation; The 2 PXXP motifs and the polyproline tract are cooperatively involved in the binding of dock/dreadlocks through its SH3 domains. PXXP motif 1 preferentially binds dock SH3 domain 1. PXXP motif 2 preferentially binds dock SH3 domain 3. The polyproline tract preferentially binds dock SH3 domain 2; The transmembrane domain is encoded by 2 mutually exclusive alternative exons, 17.1 and 17.2. Isoforms bearing the transmembrane domain encoded by exon 17.1 are targeted to dendrites while those encoded by exon 17.2 are targeted to axons.
Sequence:
MNMPNERLKWLMLFAAVALIACGSQTLAANPPDADQKGPVFLKEPTNRIDFSNSTGAEIECKASGNPMPEIIWIRSDGTAVGDVPGLRQISSDGKLVFPPFRAEDYRQEVHAQVYACLARNQFGSIISRDVHVRAVVAQYYEADVNKEHVIRGNSAVIKCLIPSFVADFVEVVSWHTDEEENYFPGAEYDGKYLVLPSGELHIREVGPEDGYKSYQCRTKHRLTGETRLSATKGRLVITEPVSSSPPKINALTYKPNIVESMASTAILCPAQGYPAPSFRWYKFIEGTTRKQAVVLNDRVKQVSGTLIIKDAVVEDSGKYLCVVNNSVGGESVETVLTVTAPLSAKIDPPTQTVDFGRPAVFTCQYTGNPIKTVSWMKDGKAIGHSEPVLRIESVKKEDKGMYQCFVRNDQESAEASAELKLGGRFDPPVIRQAFQEETMEPGPSVFLKCVAGGNPTPEISWELDGKKIANNDRYQVGQYVTVNGDVVSYLNITSVHANDGGLYKCIAKSKVGVAEHSAKLNVYGLPYIRQMEKKAIVAGETLIVTCPVAGYPIDSIVWERDNRALPINRKQKVFPNGTLIIENVERNSDQATYTCVAKNQEGYSARGSLEVQVMVPPQVLPFSFGESAADVGDIASANCVVPKGDLPLEIRWSLNSAPIVNGENGFTLVRLNKRTSLLNIDSLNAFHRGVYKCIATNPAGTSEYVAELQVNVPPRWILEPTDKAFAQGSDAKVECKADGFPKPQVTWKKAVGDTPGEYKDLKKSDNIRVEEGTLHVDNIQKTNEGYYLCEAINGIGSGLSAVIMISVQAPPEFTEKLRNQTARRGEPAVLQCEAKGEKPIGILWNMNNMRLDPKNDNRYTIREEILSTGVMSSLSIKRTERSDSALFTCVATNAFGSDDASINMIVQEVPEMPYALKVLDKSGRSVQLSWAQPYDGNSPLDRYIIEFKRSRASWSEIDRVIVPGHTTEAQVQKLSPATTYNIRIVAENAIGTSQSSEAVTIITAEEAPSGKPQNIKVEPVNQTTMRVTWKPPPRTEWNGEILGYYVGYKLSNTNSSYVFETINFITEEGKEHNLELQNLRVYTQYSVVIQAFNKIGAGPLSEEEKQFTAEGTPSQPPSDTACTTLTSQTIRVGWVSPPLESANGVIKTYKVVYAPSDEWYDETKRHYKKTASSDTVLHGLKKYTNYTMQVLATTAGGDGVRSVPIHCQTEPDVPEAPTDVKALVMGNAAILVSWRPPAQPNGIITQYTVYSKAEGAETETKTQKVPHYQMSFEATELEKNKPYEFWVTASTTIGEGQQSKSIVAMPSDQVPAKIASFDDTFTATFKEDAKMPCLAVGAPQPEITWKIKGVEFSANDRMRVLPDGSLLIKSVNRQDAGDYSCHAENSIAKDSITHKLIVLAPPQSPHVTLSATTTDALTVKLKPHEGDTAPLHGYTLHYKPEFGEWETSEVSVDSQKHNIEGLLCGSRYQVYATGFNNIGAGEASDILNTRTKGQKPKLPEKPRFIEVSSNSVSLHFKAWKDGGCPMSHFVVESKKRDQIEWNQISNNVKPDNNYVVLDLEPATWYNLRITAHNSAGFTVAEYDFATLTVTGGTIAPSRDLPELSAEDTIRIILSNLNLVVPVVAALLVIIIAIIVICILRSKGNHHKDDVVYNQTMGPGATLDKRRPDLRDELGYIAPPNRKLPPVPGSNYNTCDRIKRGRGGLRSNHSTWDPRRNPNLYEELKAPPVPMHGNHYGHAHGNAECHYRHPGMEDEICPYATFHLLGFREEMDPTKAMNFQTFPHQNGHAGPVPGHAGTMLPPGHPGHVHSRSGSQSMPRANRYQRKNSQGGQSSIYTPAPEYDDPANCAEEDQYRRYTRVNSQGGSLYSGPGPEYDDPANCAPEEDQYGSQYGGPYGQPYDHYGSRGSMGRRSIGSARNPGNGSPEPPPPPPRNHDMSNSSFNDSKESNEISEAECDRDHGPRGNYGAVKRSPQPKDQRTTEEMRKLIERNETGPKQLQLQQANGAGFTAYDTMAV