Anionic phospholipids bind to L-selectin (but not E-selectin) at a site distinct from the carbohydrate-binding site.
It is known that L-selectin binds to glycoconjugates containing the tetrasaccharide sialyl Lewis X in a Ca2+-dependent manner. In addition, a number of other acidic oligosaccharides (for example heparin or chondroitin sulphate) or glycolipids (for example sulphatides) bind to L-selectin independent of cations. In this paper we have established that L-selectin binds to charged phospholipids, such as cardiolipin and phosphatidylserine, but not to neutral phospholipids such as phosphatidylcholine. No interaction between E-selectin and any phospholipid was observed. The interaction between L-selectin cardiolipin was inhibited by dextran sulphate, fucoidan, mannose 6-phosphate and monoclonal antibodies previously reported to block the interaction between L-selectin and its natural ligands. Analysis of the amino acid sequence of the selectins indicated that L-selectin, but no E-selectin, contains a sequence homologous to the putative cardiolipin-binding epitope found in plasma glycoprotein beta2I. Glycoprotein beta2I and a peptide corresponding to the putative cardiolipin-binding epitope in beta2I inhibited the binding of L-selectin to cardiolipin or fucoidin. Based on the binding characteristics, sequence analysis and structural modelling of L-selectin, we suggest that the amino acid sequence KKNKED (residues 84-89) is a novel site for the binding of acidic species to L-selectin. This motif is localized close to the putative carbohydrate-binding domain of L-selectin and may be a second site within the lectin domain for the interaction of leucocyte L-selectin with its natural endothelial ligands.
Malhotra
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Glycobiology Research Unit and Biomolecular Structure Unit, Glaxo-Wellcome Medicines Research Centre, Stevenage, Herts., U.K.
Taylor
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NR
Bird
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D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002308:Cardiolipins / Q000378:metabolism; D019040:E-Selectin / Q000378:metabolism*; D006001:Glycoconjugates / Q000378:metabolism; D006801:Humans; D019041:L-Selectin / Q000737:chemistry / Q000378:metabolism*; D037102:Lectins / Q000737:chemistry / Q000378:metabolism; D008358:Mannose / Q000494:pharmacology; D008360:Mannosephosphates / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D000080506:Sialyl Lewis X Antigen
D002308:Cardiolipins; D019040:E-Selectin; D006001:Glycoconjugates; D037102:Lectins; D008360:Mannosephosphates; D009844:Oligosaccharides; D010743:Phospholipids; D011134:Polysaccharides; D011994:Recombinant Proteins; D000080506:Sialyl Lewis X Antigen; D019041:L-Selectin; C027693:mannose-6-phosphate; C007789:fucoidan; D008358:Mannose; D002118:Calcium