title: Functional consequences of insertions and deletions in the complementarity-determining regions of human antibodies.
abstract: Insertions and deletions of nucleotides in the genes encoding the variable domains of antibodies are natural components of the hypermutation process, which may expand the available repertoire of hypervariable loop lengths and conformations. Although insertion of amino acids has also been utilized in antibody engineering, little is known about the functional consequences of such modifications. To investigate this further, we have introduced single-codon insertions and deletions as well as more complex modifications in the complementarity-determining regions of human antibody fragments with different specificities. Our results demonstrate that single amino acid insertions and deletions are generally well tolerated and permit production of stably folded proteins, often with retained antigen recognition, despite the fact that the thus modified loops carry amino acids that are disallowed at key residue positions in canonical loops of the corresponding length or are of a length not associated with a known canonical structure. We have thus shown that single-codon insertions and deletions can efficiently be utilized to expand structure and sequence space of the antigen-binding site beyond what is encoded by the germline gene repertoire.
authors.affiliation: Department of Immunotechnology, Lund University, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Lantto
authors.forename: Mats
authors.initials: M
authors.lastname: Ohlin
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D000916:Antibody Diversity; D001666:Binding Sites, Antibody; D002942:Circular Dichroism; D022801:Complementarity Determining Regions / Q000235:genetics*; D005803:Genes, Immunoglobulin; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D000906:Antibodies; D022801:Complementarity Determining Regions; D007128:Immunoglobulin Fragments