Download MendeleyCrystal Structures of a Quorum-quenching Antibody.
Debler, E.W., Kaufmann, G.F., Kirchdoerfer, R.N., Mee, J.M., Janda, K.D., Wilson, I.A.(2007) J Mol Biol 368: 1392-1402
- PubMed: 17400249
- DOI: https://doi.org/10.1016/j.jmb.2007.02.081
- Primary Citation of Related Structures:
2NTF, 2OP4 - PubMed Abstract:
A large number of Gram-negative bacteria employ N-acyl homoserine lactones (AHLs) as signaling molecules in quorum sensing, which is a population density-dependent mechanism to coordinate gene expression. Antibody RS2-1G9 was elicited against a lactam mimetic of the N-acyl homoserine lactone and represents the only reported monoclonal antibody that recognizes the naturally-occuring N-acyl homoserine lactone with high affinity. Due to its high cross-reactivity, RS2-1G9 showed remarkable inhibition of quorum sensing signaling in Pseudomonas aeruginosa, a common opportunistic pathogen in humans. The crystal structure of Fab RS2-1G9 in complex with a lactam analog revealed complete encapsulation of the polar lactam moiety in the antibody-combining site. This mode of recognition provides an elegant immunological solution for tight binding to an aliphatic, lipid-like ligand with a small head group lacking typical haptenic features, such as aromaticity or charge, which are often incorporated into hapten design to generate high-affinity antibodies. The ability of RS2-1G9 to discriminate between closely related AHLs is conferred by six hydrogen bonds to the ligand. Conversely, cross-reactivity of RS2-1G9 towards the lactone is likely to originate from conservation of these hydrogen bonds as well as an additional hydrogen bond to the oxygen of the lactone ring. A short, narrow tunnel exiting at the protein surface harbors a portion of the acyl chain and would not allow entry of the head group. The crystal structure of the antibody without its cognate lactam or lactone ligands revealed a considerably altered antibody-combining site with a closed binding pocket. Curiously, a completely buried ethylene glycol molecule mimics the lactam ring and, thus, serves as a surrogate ligand. The detailed structural delineation of this quorum-quenching antibody will aid further development of an antibody-based therapy against bacterial pathogens by interference with quorum sensing.
Organizational Affiliation:
Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
