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Antigen‐antibody interactions: Elucidation of the epitope and strain‐specificity of a monoclonal antibody directed against the pilin protein adherence binding domain of Pseudomonas aeruginosa strain K
Author(s) -
Wong Wah Y.,
Irvin Randall T.,
Paranchych William,
Hodges Robert S.
Publication year - 1992
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560011010
Subject(s) - epitope , pilin , monoclonal antibody , pilus , peptide , peptide sequence , conformational epitope , chemistry , antibody , linear epitope , biochemistry , epitope mapping , microbiology and biotechnology , biology , escherichia coli , genetics , gene
The C‐terminal region of Pseudomonas aeruginosa strain K (PAK) pilin comprises both an epitope for the strain‐specific monoclonal antibody PK99H, which blocks pilus‐mediated adherence, and the adherence binding domain for buccal and tracheal epithelial cells. The PK99H epitope was located in sequence 134–140 (Asp‐Glu‐Gln‐Phe‐Ile‐Pro‐Lys) by using a single alanine replacement analysis on the 17‐residue synthetic peptide corresponding to the PAK C‐terminal sequence 128–144. Indeed, a 7‐residue peptide corresponding to this sequence was shown to have a similar binding affinity to that of the native conformationally constrained (disulfide bridged) 17‐residue peptide. This epitope was found to contain two critical residues (Phe 137 and Lys 140 ) and one nonessential residue (Gln 136 ). Interestingly, the peptide, Phe‐Ile‐Pro‐Lys, which constitutes the four most important side chains for antibody binding did not bind to PK99H. It was of interest to investigate the structural basis of the strain‐specificity of PK99H utilizing naturally occurring pilin sequences. Therefore, all different residues found in the sequence corresponding to the PK99H epitope of the four other strains (PAO, CD4, K122–4, and KB7) were substituted one at a time in the PAK sequence and the changes in binding affinity of these analogs to the antibody PK99H were determined by competitive ELISA. The strain‐specificity of PK99H for strains PAO, K122–4, and KB7 can be explained by the accumulated sequence changes in these strains, and at least two amino acid changes were required to explain the strain‐specificity of PK99H. Similarly, cross‐reactivity of PK99H with CD4 can be explained by the fact that there was only one side chain responsible for decreasing binding affinity compared to the PAK sequence.