Highly specific anti-estradiol antibodies: structural characterisation and binding diversity

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• Antibody-antigen recognition is crucial for protein engineering.
• Understanding antibody binding properties requires accurate structural and energetic descriptions.

Purpose of the Study:

• To determine the crystal structure of two anti-estradiol monoclonal antibodies (10G6D6 and 17E12E5).
• To guide protein engineering for increased affinity and specificity towards natural estradiol over its immunogen.

Main Methods:

• X-ray crystallography was used to determine the structures of anti-estradiol antibodies.
• Structural analysis focused on binding pocket characteristics and steroid positioning.
• Identification of specific antibody-antigen contacts, including linker interactions.

Main Results:

• Two anti-estradiol antibodies, 10G6D6 and 17E12E5, exhibit dissimilar binding pockets and steroid orientations despite similar origins.
• The 17-hydroxyl group is consistently buried in hydrophobic pockets and stabilized by hydrogen bonds.
• High antibody specificity was observed, with low cross-reactivity to related steroids.
• Specific contacts between the 6-CMO linker and an arginine residue in antibody 10G6D6 were identified.

Conclusions:

• Structural insights into antibody-estradiol interactions provide a basis for protein engineering.
• Targeting specific antibody regions, like CDR2, can be used to select for improved estradiol binding.
• These findings facilitate the development of antibodies with enhanced specificity for natural estradiol.