Dec 2, 1975

Conformational changes induced in a homogeneous anti-type III pneumococcal antibody by oligosaccharides of increasing size

Biochemistry
J C JatonJ Schlessinger

Abstract

The circular polarization of luminescence (CPL) emitted by tryptophan residues was used as a sensitive probe for measuring ligand-induced structural changes in a homogeneous type III pneumococcal antibody. A series of oligosaccharide ligands of increasing size derived from type III polysaccharide by partial acid hydrolysis was assayed. Ligand-induced changes in the circular polarization of fluorescence of the antibody were observed for all antigens tested, including tetra-, hexa-, and octasaccharides and a 16-residue oligomer, the largest changes being recorded upon interaction with the intact soluble type III pneumococcal (SIII) polysaccharide. When Fab' or F(ab')2 fragments were used instead of the antibody IgG for binding of SIII polysaccharide, the extent of conformational changes was decreased. This suggests interactions between Fab and Fc portions in the IgG molecule and subsequent conformational changes in Fc part upon antigen binding. Reduction of interchain disulfide bonds abolished the additional spectral changes attributed to the Fc part but not the changes observed in the Fab part, thus suggesting that the presence of the interchain disulfide bond in the hinge region is required for maximal CPL changes to occur. Sma...Continue Reading

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Mentioned in this Paper

Tryptophan
Antigen Binding
Structure-Activity Relationship
TCEB1 gene
Triportheus paranensis
TCEB3 gene
Fab Immunoglobulins
Polysaccharides, Bacterial
Soluble
Antigens

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