Interaction of a bacterially expressed peptide from the receptor binding domain of Pseudomonas aeruginosa pili strain PAK with a cross-reactive antibody: conformation of the bound peptide.
The C-terminal receptor binding region of Pseudomonas aeruginosa pilin protein strain PAK (residues 128-144) has been the target for the design of a vaccine effective against P. aeruginosa infections. We have recently cloned and expressed a (15)N-labeled PAK pilin peptide spanning residues 128-144 of the PAK pilin protein. The peptide exists as a major (trans) and minor (cis) species in solution, arising from isomerization around a central Ile(138)-Pro(139) peptide bond. The trans isomer adopts two well-defined turns in solution, a type I beta-turn spanning Asp(134)-Glu-Gln-Phe(137) and a type II beta-turn spanning Pro(139)-Lys-Gly-Cys(142). The cis isomer adopts only one well-defined type II beta-turn spanning Pro(139)-Lys-Gly-Cys(142) but displays evidence of a less ordered turn spanning Asp(132)-Gln-Asp-Glu(135). These turns have been implicated in cross-reactive antibody recognition. (15)N-edited NMR spectroscopy was used to study the binding of the (15)N-labeled PAK pilin peptide to an Fab fragment of a cross-reactive monoclonal antibody, PAK-13, raised against the intact PAK pilus. The results of these studies are as follows: the trans and cis isomers bind with similar affinity to the Fab, despite their different topologies; both isomers maintain the conformational integrity of their beta-turns when bound; binding leads to the preferential stabilization of the first turn over the second turn in each isomer; and binding leads to the perturbation of resonances within regions of the trans and cis backbone that undergo microsecond to millisecond motions. These slow motions may play a role in induced fit binding of the first turn to Fab PAK-13, which would allow the same antibody combining site to accommodate either trans or cis topology. More importantly for vaccine design, these motions may also play a role in the development of a broad-spectrum vaccine capable of generating an antibody therapeutic effective against the multiple strains of P. aeruginosa.
Campbell
A P
AP
Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, Washington 98195, USA. apc@u.washington.edu
Wong
W Y
WY
Irvin
R T
RT
Sykes
B D
BD
D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000737:chemistry / Q000276:immunology*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology*; D001428:Bacterial Vaccines / Q000737:chemistry / Q000276:immunology*; D001665:Binding Sites; D003429:Cross Reactions; D015195:Drug Design; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000276:immunology*; D007536:Isomerism; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology*; D008969:Molecular Sequence Data; D009038:Motion; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000276:immunology*
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D008565:Membrane Proteins; D010446:Peptide Fragments; D036781:Fimbriae Proteins