Structure of antibodies

Structure of antibodies

Edelman and Porter (1969) first established the chemical nature of immunoglobulins.
These are Y-shaped globular protein, (glycoprotein-mol. wt. 1,50,000).
Mol. wt. of Light chain (LC) is 25,000 each and of Heavy chain (HC) is 50,000 each.
Number of amino acid in LC is 50 and 100 in HC. LC and HC are linked by disulphide bond.
Molecule has two parts : upper V (variable) region and lower C (constant) region.
The V-region has both light and heavy chains while C-region is made of only heavy chain. C-region is constant for all types of antibodies.
Treatment with papain enzyme cleaves the fragments as lower Fc (Fragment crystallisable) and the upper two branches as Fab.
Each Fab (Fragment antigen binding) branch has one antigen binding site at the amino (–NH₂) terminal of the chain.

Fig. Structure of immunoglobulin