A New Pathway for Protein Haptenation by beta-Lactams

Autores de IIS La Fe

• Inmaculada Andreu Ros

  Autor

• Miguel Ángel Miranda Alonso

  Autor

• María Consuelo Jiménez Molero

  Autor

Participantes ajenos a IIS La Fe

• Perez-Ruiz, Raul
• Lence, Emilio
• Limones-Herrero, Daniel
• Gonzalez-Bello, Concepcion

Grupos

• Unidad Mixta de Investigación en Mecanismos moleculares de las Reacciones adversas de fármacos

Abstract

The covalent binding of beta-lactams to proteins upon photochemical activation has been demonstrated by using an integrated approach that combines photochemical, proteomic and computational studies, selecting human serum albumin (HSA) as a target protein and ezetimibe (1) as a probe. The results have revealed a novel protein haptenation pathway for this family of drugs that is an alternative to the known nucleophilic ring opening of beta-lactams by the free amino group of lysine residues. Thus, photochemical ring splitting of the beta-lactam ring, following a formal retro-Staudinger reaction, gives a highly reactive ketene intermediate that is trapped by the neighbouring lysine residues, leading to an amide adduct. For the investigated 1/HSA system, covalent modification of residues Lys414 and Lys525, which are located in sub-domains IIIA and IIIB, respectively, occurs. The observed photobinding may constitute the key step in the sequence of events leading to photoallergy. Docking and molecular dynamics simulation studies provide an insight into the molecular basis of the selectivity of 1 for these HSA sub-domains and the covalent modification mechanism. Computational studies also reveal positive cooperative binding of sub-domain IIIB that explains the experimentally observed modification of Lys414, which is located in a barely accessible pocket (sub-domain IIIA).

Keywords

• allergy; lactams; molecular dynamics; photochemistry; proteins