Antibody CDR H3 modeling rules: extension for the case of absence of Arg H94 and Asp H101

Area of Science:

• Immunology
• Structural Biology
• Computational Biology

Background:

• The third complementary determining region (CDR H3) of the immunoglobulin heavy chain presents modeling challenges due to its genetic variability.
• The conformation of the CDR H3 "torso" region is generally predictable, with current theories focusing on key residues at positions H94 and H101.
• Predictive models exist for CDR H3 torso structures when specific residues (arginine, lysine, or aspartic acid) are present at H94 and/or H101.

Purpose of the Study:

• To investigate and establish sequence-structure rules for CDR H3 conformations in cases lacking key residues at positions H94 and H101.
• To address a gap in the literature concerning the modeling of CDR H3 structures with uncharacteristic residue combinations at critical positions.
• To enhance the accuracy of antibody structure modeling by developing new predictive rules.

Main Methods:

• Analysis of 51 CDR H3 structures lacking key residues at positions H94 and H101.
• Identification and establishment of novel sequence-structure relationships specific to these CDR H3 variants.
• Development of new rules to guide the prediction of CDR H3 torso conformations.

Main Results:

• New sequence-structure rules were successfully established for CDR H3 regions lacking key residues at H94 and H101.
• The study identified predictable conformational patterns in CDR H3 despite the absence of canonical residues.
• These findings provide a basis for more accurate modeling of previously intractable CDR H3 structures.

Conclusions:

• The established rules offer improved predictability for CDR H3 "torso" conformations in specific, understudied cases.
• This research contributes to more accurate antibody structure modeling, particularly for antibodies with atypical CDR H3 sequences.
• The findings advance the understanding of CDR H3 structure-function relationships and antibody engineering.