| Abstract
| - Protein−carbohydrate interactions are known to mediatecell−cell recognition and adhesionevents. Specifically, three carbohydrate binding proteins termedselectins (E-, P-, and L-selectin) havebeen shown to be essential for leukocyte rolling along the vascularendothelium, the first step in therecruitment of leukocytes from the blood into inflammatory sites orinto secondary lymphoid organs.Although this phenomenon is well-established, little is knownabout the molecular-level interactions onwhich it depends. All three selectins recognize sulfated andsialylated derivatives of the Lewis x [Lex: Galβ1→4(Fucα1→3)GlcNAc] and Lewis a[Lea: Galβ1→3(Fucα1→4)GlcNAc]trisaccharide cores withaffinities in the millimolar range, and it is believed that variants ofthese structures are the carbohydratedeterminants of selectin recognition. Recently it was shown thatthe mucin GlyCAM-1, a secretedphysiological ligand for L-selectin, is capped with sulfatedderivatives of sialyl Lewis x [sLex: Siaα2→3Galβ1→4(Fucα1→3)GlcNAc] and thatsulfation is required for the high-affinity interactionbetween GlyCAM-1 and L-selectin. To elucidate the important sitesof sulfation on Lex with respect toL-selectin recognition, we have synthesized six sulfatedLex analogs and determined their abilities toblock binding of a recombinant L-selectin−Ig chimera to immobilizedGlyCAM-1. Our results suggestthat 6-sulfo sLex binds to L-selectin with higher affinitythan does sLex or 6‘-sulfo sLex and thatsulfationof sLex capping groups on GlyCAM-1 at the 6-position isimportant for L-selectin recognition.
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