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Title
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Ligand binding by the immunoglobulin superfamily recognition molecule CD2 is glycosylation-independent.
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Authors
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S.J.Davis,
E.A.Davies,
A.N.Barclay,
S.Daenke,
D.L.Bodian,
E.Y.Jones,
D.I.Stuart,
T.D.Butters,
R.A.Dwek,
P.A.van der Merwe.
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Ref.
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J Biol Chem, 1995,
270,
369-375.
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PubMed id
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Abstract
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The evolutionary success of the immunoglobulin superfamily (IgSF) is thought to
reflect the ability of IgSF protein domains to form stable structural units. The
role of glycosylation in stabilizing these domains is controversial, however. In
this study a systematic analysis of the effect of glycosylation on the
ligand-binding properties of the cell-cell recognition molecule CD2, which
consists of two IgSF domains, was undertaken. A form of human soluble CD2
(hsCD2) with single N-acetylglucosamine residues at each glycosylation site was
produced by inhibiting glucosidase I with N-butyldeoxynojirimycin during
expression in Chinese hamster ovary cells and digesting the expressed hsCD2 with
endoglycosidase H. The ligand and antibody binding properties of this form of
hsCD2 were indistinguishable from those of fully glycosylated hsCD2 as
determined by surface plasmon resonance analyses. The protein also formed
diffraction quality crystals and analysis of the 2.5-A resolution crystal
structure indicated that the single N-acetylglucosamine residue present on
domain 1 is unlikely to stabilize the ligand binding face of hsCD2. A second,
fully deglycosylated form of hsCD2 also bound the ligand and antibodies although
this form of the protein tended to aggregate. In contrast to the results of
previous studies, the current data indicate that the structural integrity and
ligand binding function of human CD2 are glycosylation-independent.
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