Master the Enzymatic Mechanisms of V(D)J Recombination

V(D)J Recombination

• The rule for V-region rearrangement in DNA recombination is that it occurs randomly, resulting in a unique sequence for each B cell.
• During V(D)J recombination, the DNA molecule is rearranged, and the intervening DNA is deleted, forming a circular DNA molecule.
• The double-heptamer sequence created in V(D)J recombination serves as a recognition sequence for the recombination machinery.
• When the joining segments are in the same orientation, the signal joint is deleted, and the coding joints are joined.
• The V and J gene segments form a continuous VJ exon after V(D)J recombination.

Immunoglobulin Structure

• The variable regions of immunoglobulin heavy and light chains are based on the immunoglobulin fold structure.
• The antibody-binding site is formed by the hypervariable regions (HV).
• The HV loops that form the antibody-binding site are located at the tips of the immunoglobulin fold.
• The first exon of the variable regions encodes the leader sequence and the HV1, HV2, and HV3 regions.
• The leader sequence is responsible for targeting the protein to the endoplasmic reticulum for synthesis.
• The immunoglobulin fold consists of a beta-sheet structure with a specific arrangement of disulfide bonds.
• The variable regions play a crucial role in a mature B cell, as they determine the specificity of the antibody.

Hypervariable Regions

• The HV1, HV2, and HV3 regions are also known as complementarity-determining regions (CDRs).
• The first exon of the variable regions encodes the HV1, HV2, and HV3 regions.
• The HV loops are located at the tips of the immunoglobulin fold, forming the antibody-binding site.