IL-2, a lectin with specificity for high mannose glycopeptides.
Utilizing a solid phase binding assay, we have demonstrated that rIL-2 binds with high affinity to the human urinary glycoprotein uromodulin. This binding is specifically inhibited by the saccharides diacetylchitobiose and Man(alpha 1-3)(Man(alpha 1-6]Man-O-methyl and by the high mannose glycopeptides Man5GlcNAc2-R and Man6GlcNAc2-R, but not by Man9GlcNAc2-R. rIL-2 also binds OVA, a glycoprotein which contains approximately 50% high mannose chains at a single glycosylation site, and to yeast mannan. This binding is inhibited by the same battery of saccharides which inhibit the binding to uromodulin. The conclusion that rIL-2 is a lectin is further supported by the observation that the sequence of IL-2 shares 27% homology with a 33-residue sequence of the carbohydrate-binding domain of human mannose-binding protein. The potential physiologic relevance of the carbohydrate binding activity is further elucidated by studies which show that 1) binding of soluble rIL-2 to immobilized uromodulin is enhanced at a pH of 4 to5 in the presence of divalent cations, and 2) neither uromodulin nor the high mannose glycopeptide Man5GlcNAc2Asn blocks the binding of rIL-2 to the IL-2R. Thus the carbohydrate-binding site of rIL-2 is distinct from the cell surface receptor-binding site, and might function preferentially in acidic microenvironments.
Sherblom
A P
AP
Department of Biochemistry, University of Maine, Orono 04469.
Sathyamoorthy
N
N
Decker
J M
JM
Muchmore
A V
AV
D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002240:Carbohydrate Sequence; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D006020:Glycopeptides / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007376:Interleukin-2 / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism* / Q000494:pharmacology; D037241:Mannose-Binding Lectins; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000378:metabolism; D009844:Oligosaccharides / Q000494:pharmacology; D011247:Pregnancy; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D058949:Uromodulin
D002352:Carrier Proteins; D006020:Glycopeptides; D007376:Interleukin-2; D037102:Lectins; D037241:Mannose-Binding Lectins; D009088:Mucoproteins; D009844:Oligosaccharides; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; C548612:UMOD protein, human; D058949:Uromodulin; D008358:Mannose