1970 Kabat proposed the hypervariable regions segments form the antigen-binding site. V region of light chain is similar to the V region of heavy chain. C region of light chain resembels the repeating constant regions of the heavy chain. E. X-Ray Analysis of Fab has been solved 1. Units of similar structure arranged in a tetrahedral array of four globular units.
Fc region shows similar structures.
The repetitive strukctural core of the immunoglobin domains are two broad sheets of antiparallel beta strands - called the immunoglobin fold. X-ray analysis shows that hypervariable sequences are located in loops at the end of one sandwich. The immunoglobin core provides a framework which allows almost infinite variations in the loops. Since any light chain variable region can combine with any variable region on a heavy chain, the large number of potential binding sites is very high. From protein sequences found mRNA of an immunoglobin 1.