Structural and biochemical differences between non-catalytic and catalytic antibodies

Area of Science:

• Biochemistry
• Structural Biology
• Immunology

Background:

• Conventional antibodies can be engineered into catalytic counterparts.
• The deletion of Pro95 in the CDR-3 region of antibody light chains has been previously reported to confer catalytic activity.

Purpose of the Study:

• To elucidate the structural basis for enzymatic function acquisition in catalytic antibodies engineered by Pro95 deletion.
• To investigate the catalytic activity of a naturally occurring human antibody light chain (T99wt) and its engineered variant (T99-Pro95(-)) against synthetic peptides and amyloid-beta.

Main Methods:

• X-ray crystallography was employed to determine the structural changes upon Pro95 deletion.
• Molecular dynamics (MD) simulations were used to analyze the dynamic behavior and active site formation.

Main Results:

• Pro95 deletion in T99wt significantly reduced the distance between key catalytic residues Asp1 and His93, facilitating active site formation.
• The engineered T99-Pro95(-) variant exhibited enhanced catalytic activity, effectively cleaving both Arg-pNA and amyloid-beta peptides.
• MD simulations revealed transient proximity of catalytic residues (Asp1, His93, Ser27a) upon Pro95 removal, enabling a functional catalytic triad.

Conclusions:

• Pro95 deletion is a key modification for converting conventional antibodies into efficient catalytic antibodies.
• This finding represents a significant technological advancement for generating catalytic antibodies from known sequences.