Identification of a serine protease inhibitor homologue in Bird's Nest by an integrated proteomics approach

For centuries, the edible nests of Collocalia spp. ("Bird's Nests") have be en used as a Chinese delicacy that had been claimed to be an effective heal th-giving tonic, However, clinical studies indicated that in Singapore, Bir d's Nest is the most common cause of food-induced anaphylaxis in children, which could lead to potentially life-threatening allergenic reactions. The purpose of this study was to characterize the major allergens in Bird's Nes t by using the combined technologies of two-dimensional gel electrophoresis (2-DE), immunochemistry, N-terminal protein sequencing, and mass spectrome try Results from the immunostaining of the Western blots of the Bird's Nest 2-DE separated proteins with the sera from allergic patients indicated the presence of a major allergen of 66 kDa. Initial searches of the matrix ass isted laser desorption/ionization - time of flight - mass spectrometry (MAL DI-TOF-MS) tryptic peptide masses of the allergen in the SWISS-PROT and NCB I nonredundant databases revealed that this protein was novel. Based on the partial protein sequence information obtained from N-terminal microsequenc ing and nanoelectrospray-tandem MS, the 66 kDa immunoreactive allergen was found to be homologous to ovoinhibitor, a Kazal-type serine protease inhibi tor, which is one of the dominant allergens found in chicken egg white.