Progress towards the Mass Spectrometric Determination of the N- and C-termini of Zona Pellucida Glycoproteins from X. Iaevis eggs

摘要

The extracellular glycoprotein matrix of mature unfertilized Xenopus laevis eggs, which is called the vitelline envelope (VE), plays an important role in the specific sperm-egg binding during fertilization and in the protection of the early embryo. The VE consists of at least 5 zona pellucida (ZP) glycoproteins: ZPA (64/69 kDa), ZPB (37 kDa), ZPC (41 kDa), ZPD (80 kDa) and ZPX (112/120 kDa) [1]. The oligosaccharides on ZPA and ZPC have been shown to possess sperm binding activity. All these ZP glycoproteins have been cloned, and the sequences and N- and C-termini of the glycoproteins need to be confirmed by alternative methods. Among these glycoproteins, the N- and C-termini of ZPB and ZPC have been confirmed in our lab with MALDI-TOF and MALDI-QIT-TOF mass spectrometry. The objective here was to demonstrate a convenient mass spectrometric method for the determination of N- and C-termini through trypsin digestion in the presence of ~(18)O-water.