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Conformation of the hypervariable region L3 without the key proline residue
Protein Science : a Publication of the Protein Society
|January 1, 1996
Summary
The crystal structure of a monoclonal antibody fragment (Fab) targeting CD5 reveals a novel conformation in its light chain, crucial for understanding antibody function in approximately 10% of kappa light chain IgG molecules.
Area of Science:
- Immunology
- Structural Biology
- Biochemistry
Background:
- Monoclonal antibodies are vital tools in research and therapeutics.
- Antibody structure, particularly complementarity determining regions (CDRs), dictates antigen binding.
- The kappa light chain's CDR-L3 conformation is critical but not fully understood.
Purpose of the Study:
- To elucidate the three-dimensional structure of the Fab fragment of the CRIS-I antibody.
- To investigate the conformation of the light chain CDR-L3 in an antibody lacking key proline residues.
- To assess the structural implications for murine immunoglobulin G (IgG) molecules.
Main Methods:
- X-ray crystallography was used to determine the structure.
- High-resolution (1.9 Å) structural analysis was performed.
- The agreement R-factor was 18.3%.
Main Results:
- The refined structure of the CRIS-I Fab fragment was determined.
- A novel conformation of the CDR-L3 was observed in the kappa light chain.
- This CDR-L3 lacked proline residues at positions 94 or 95, a first for a kappa light chain Fab structure.
Conclusions:
- The identified CDR-L3 conformation represents a variant of canonical models.
- This finding is significant for understanding the structure-function relationship of approximately 10% of murine IgG molecules with kappa light chains.
- The study provides new insights into antibody structural diversity.