Hypervariable Regions

Hypervariable Regions

Hypervariable Regions

Some parts of the variable regions are more variable than others, and are known as hyper variable regions. The hyper variable regions of both light and heavy chains are believed to form the antigen binding sites. The hyper variable amino acids surround a cavity between the VL and VH regions. The antigen fits into this cavity. The hyper variable regions contain about a third of the amino acids of the variable regions

The hyper variable regions in turn contain certain regions called hot spots, which have different amino acid residues in different antibodies. The other amino acids in the variable region are relatively constant in the different antibodies. This constancy is probably necessary for the basic folding of the immunoglobulin molecule. Glycine residues commonly occur in the variable region.

Glycine is found in several positions near the hyper variable regions, and invariably occurs near a hot spot. Glycine has no side chain cause stearic hindrance, and favours disruption of helices. Its presence would, therefore, give freedom for the orientation of hyper variable residues, permitting them to form groups for binding particular antigen.

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