Final answer:
The heavy chain 'V' region of an antibody contains three hypervariable regions: CDR1 (residues 31 to 37), CDR2 (residues 51 to 68), and CDR3 (residues 86 to 109). These regions enable antigen binding and are supported by more conserved framework regions.
Step-by-step explanation:
The variable ('V') region of the heavy chain of an antibody, specifically the immunoglobulin, is characterized by different encoded sections known as the hypervariable regions or complementarity determining regions (CDRs). The heavy chain's V region is composed of three CDRs, each reflecting a section of the polypeptide chain where there's a high degree of variability in the amino acid sequence, enabling the antibody to bind to a diverse array of antigens. The three hypervariable regions of the heavy chain are:
- CDR1: Spans from residues 31 to 37.
- CDR2: Extends from residues 51 to 68.
- CDR3: Located between residues 86 to 109.
These regions are held in place by more conserved sequences known as framework regions, which make up 80-85% of the variable region. The CDRs are instrumental in forming the antigen-binding site of the antibody when they are brought together with the hypervariable regions of the light chain.
The heavy chain is part of a larger structure that includes constant (C) regions designated as CH1, CH2, and CH3 (and sometimes a fourth, CH4), which are responsible for mediating immune responses. The complete heavy chain, consisting of both variable and constant regions, contributes to the overall Y-structured antibody, capable of specific antigen recognition and effector functions.