Phage display and peptide mapping of an immunoglobulin light chain fibril-related conformational epitope.
Amyloid fibrils and partially unfolded intermediates can be distinguished serologically from native amyloidogenic precursor proteins or peptides. In this regard, we previously had reported that mAb 11-1F4, generated by immunizing mice with a thermally denatured variable domain (VL) fragment of the human kappa4 Bence Jones protein Len, bound to a non-native conformational epitope located within the N-terminal 18 residues of fibrillar, as well as partially denatured, Ig light chains (O'Nuallain, B., et al. (2006) Biochemistry 46, 1240-1247). To define further the antibody binding site, we used random peptide phage display and epitope mapping of VL Len using wild-type and alanine-mutated Len peptides where it was shown that the antibody epitope was reliant on up to 10 of the first 15 residues of protein Len. Comparison of Vkappa and Vlambda N-terminal germline consensus sequences with protein Len and 11-1F4-binding phages indicated that this antibody's cross-reactivity with light chains was related to an invariant proline at position(s) 7 and/or 8, bulky hydrophobic residues at positions 11 and 13, and additionally, to the ability to accommodate amino acid diversity at positions 1-4. Sequence alignments of the phage peptides revealed a central proline, often flanked by aromatic residues. Taken together, these results have provided evidence for the structural basis of the specificity of 11-1F4 for both kappa and lambda light chain fibrils. We posit that the associated binding site involves a rare type VI beta-turn or touch-turn that is anchored by a cis-proline residue. The identification of an 11-1F4-related mimotope should facilitate development of pan-light chain fibril-reactive antibodies that could be used in the diagnosis and treatment of patients with AL amyloidosis.
O'Nuallain
Brian
B
Human Immunology and Cancer/Alzheimer's Disease and Amyloid-Related Disorders Research Program, Department of Medicine, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee 37920, USA.
Allen
Amy
A
Ataman
Demet
D
Weiss
Deborah T
DT
Solomon
Alan
A
Wall
Jonathan S
JS
D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry* / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D001536:Bence Jones Protein / Q000737:chemistry / Q000276:immunology; D018604:Epitope Mapping; D000939:Epitopes; D007147:Immunoglobulin Light Chains / Q000737:chemistry*; D019151:Peptide Library; D011487:Protein Conformation; D016415:Sequence Alignment
D000682:Amyloid; D000911:Antibodies, Monoclonal; D000939:Epitopes; D007147:Immunoglobulin Light Chains; D019151:Peptide Library; D001536:Bence Jones Protein