A simple characterization of special matchings in lower Bruhat intervals

We give a simple characterization of special matchings in lower Bruhat intervals (that is, intervals starting from the identity element) of a Coxeter group. As a byproduct, we obtain some results on the action of special matchings.Comment: accepted for publication on Discrete Mathematic

Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family

<p>Abstract</p> <p>Background</p> <p>The first step of GPI anchor biosynthesis is catalyzed by PIG-A, an enzyme that transfers <it>N</it>-acetylglucosamine from UDP-<it>N</it>-acetylglucosamine to phosphatidylinositol. This protein is present in all eukaryotic organisms ranging from protozoa to higher mammals, as part of a larger complex of five to six 'accessory' proteins whose individual roles in the glycosyltransferase reaction are as yet unclear. The PIG-A gene has been shown to be an essential gene in various eukaryotes. In humans, mutations in the protein have been associated with paroxysomal noctural hemoglobuinuria. The corresponding PIG-A gene has also been recently identified in the genome of many archaeabacteria although genes of the accessory proteins have not been discovered in them. The present study explores the evolution of PIG-A and the phylogenetic relationship between this protein and other glycosyltransferases.</p> <p>Results</p> <p>In this paper we show that out of the twelve conserved motifs identified by us eleven are exclusively present in PIG-A and, therefore, can be used as markers to identify PIG-A from newly sequenced genomes. Three of these motifs are absent in the primitive eukaryote, <it>G. lamblia</it>. Sequence analyses show that seven of these conserved motifs are present in prokaryote and archaeal counterparts in rudimentary forms and can be used to differentiate PIG-A proteins from glycosyltransferases. Using partial least square regression analysis and data involving presence or absence of motifs in a range of PIG-A and glycosyltransferases we show that (i) PIG-A may have evolved from prokaryotic glycosyltransferases and lipopolysaccharide synthases, members of the GT4 family of glycosyltransferases and (ii) it is possible to uniquely classify PIG-A proteins versus glycosyltransferases.</p> <p>Conclusion</p> <p>Besides identifying unique motifs and showing that PIG-A protein from <it>G. lamblia </it>and some putative PIG-A proteins from archaebacteria are evolutionarily closer to glycosyltransferases, these studies provide a new method for identification and classification of PIG-A proteins.</p

Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family-1

Rged away from other eukaroyotic PIG-A proteins.<p><b>Copyright information:</b></p><p>Taken from "Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family"</p><p>http://www.biomedcentral.com/1471-2148/8/168</p><p>BMC Evolutionary Biology 2008;8():168-168.</p><p>Published online 4 Jun 2008</p><p>PMCID:PMC2446393.</p><p></p

Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family-6

. Three of these motifs are absent in .<p><b>Copyright information:</b></p><p>Taken from "Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family"</p><p>http://www.biomedcentral.com/1471-2148/8/168</p><p>BMC Evolutionary Biology 2008;8():168-168.</p><p>Published online 4 Jun 2008</p><p>PMCID:PMC2446393.</p><p></p

Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family-7

Rged away from other eukaroyotic PIG-A proteins.<p><b>Copyright information:</b></p><p>Taken from "Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family"</p><p>http://www.biomedcentral.com/1471-2148/8/168</p><p>BMC Evolutionary Biology 2008;8():168-168.</p><p>Published online 4 Jun 2008</p><p>PMCID:PMC2446393.</p><p></p

Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family-4

Rom eukaryotes are evolutionarily a separate branch of proteins.<p><b>Copyright information:</b></p><p>Taken from "Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family"</p><p>http://www.biomedcentral.com/1471-2148/8/168</p><p>BMC Evolutionary Biology 2008;8():168-168.</p><p>Published online 4 Jun 2008</p><p>PMCID:PMC2446393.</p><p></p

Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family-8

appears to be closer to the archaeal proteins than to other eukaryotic PIG-A proteins.<p><b>Copyright information:</b></p><p>Taken from "Unique motifs identify PIG-A proteins from glycosyltransferases of the GT4 family"</p><p>http://www.biomedcentral.com/1471-2148/8/168</p><p>BMC Evolutionary Biology 2008;8():168-168.</p><p>Published online 4 Jun 2008</p><p>PMCID:PMC2446393.</p><p></p