Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.7 (acetylcholinesterase)
 28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RT6 is an unusual cell membrane protein that is expressed exclusively by postthymic T cells. The inherent defect in its expression has been correlated to lymphopenia and genetically determined susceptibility for insulin-dependent diabetes mellitus in the rat. We report here the primary structure of the RT6.2 alloantigen as deduced from the cDNA sequence. The predicted amino acid sequence of RT6.2 begins with a conventional leader of 20 amino acids and ends in a hydrophobic C-terminal extension peptide of 29 amino acids as is common for phosphatidylinositol-anchored proteins. Native RT6.2 is predicted to comprise 226 amino acids, with a calculated Mr of 26,036. Four cysteine residues account for two intrachain disulfide bonds. The sequence lacks potential N-glycosylation sites and contains an excess of positively charged residues. Homology searches in protein sequence data banks suggest that RT6.2 is not encoded by a member of the immunoglobulin supergene family. Moreover, these analyses did not reveal any close homologies of RT6.2 to known proteins: the highest homology found was 21.2% identity in a 52-amino acid overlap to the torpedo acetylcholinesterase precursor. Southern blot analyses indicate that RT6.2 is the product of a single-copy gene and provide evidence for closely related genes in the mouse and other species. The corresponding gene products remain to be identified.
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PMID:Primary structure of rat RT6.2, a nonglycosylated phosphatidylinositol-linked surface marker of postthymic T cells. 230 May 88

Decay-accelerating factor (DAF) is an integral membrane protein that inhibits amplification of the complement cascade on the cell surface. We and other investigators have shown that DAF is part of a newly characterized family of proteins that are anchored to the cell membrane by phosphatidylinositol (PI). The group includes the variant surface glycoprotein (VSG) of African trypanosomes, the p63 protein of Leishmania, acetylcholinesterase (AChE), alkaline phosphatase, Thy-1, 5'-nucleotidase, and RT6.2--an alloantigen from rat T cells. The structure of the membrane anchor has been best characterized for VSG, but chemical studies of the membrane anchors of AChE and Thy-1 suggest that similar glycolipid moieties anchor these proteins to the cell surface. In the VSG, the membrane anchor consists of an ethanolamine linked covalently to an oligosaccharide and glucosamine; the entire complex is anchored to the cell membrane by PI. Immunologically, this glycolipid defines an epitope, the cross-reacting determinant (CRD), that is only revealed after removal of the diacyl glycerol anchor by a phospholipase C. By Western blotting, we show here that DAF-S (DAF released from the membrane by PI-specific phospholipase C [PIPLC]) also contains CRD. Using a newly developed immunoradiometric assay (IRMA) in which the solid-phase capturing antibody is a monoclonal antibody to DAF and the second antibody is anti-CRD, we have been able to quantitate DAF-S. By IRMA, we show that the reaction between anti-CRD and DAF-S is specific, since the binding is competitively inhibited only by the soluble form of the VSG. These observations further support the concept that the glycolipid anchors of this new family of proteins have similar structures. DAF is also found as a soluble protein in various tissue fluids as well as in Hela cell supernatants. No evidence for the presence of the CRD epitope was found on these proteins, suggesting that these forms of DAF are not released from the surface of cells by endogenous phospholipases.
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PMID:Decay-accelerating factor (DAF) shares a common carbohydrate determinant with the variant surface glycoprotein (VSG) of the African Trypanosoma brucei. 243 27