N- and O-linked glycosylation site profiling of the human basic salivary proline-rich protein 3M

MANCONI, BARBARA;CABRAS, TIZIANA;SANNA, MONICA;PIRAS, VALENTINA;LIORI, BARBARA;PISANO, ELISABETTA;Iavarone, Federica;Vincenzoni, Federica;Cordaro, Massimo;FAA, GAVINO;Castagnola, Massimo;MESSANA, IRENE

2016-01-01

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Abstract

In the present study, we show that the heterogeneous mixture of glycoforms of the basic salivary proline-rich protein 3M, encoded by PRB3-M locus, is a major component of the acidic soluble fraction of human whole saliva in the first years of life. Reversed-phase high-performance liquid chromatography with high-resolution electrospray ionization mass spectrometry analysis of the intact proteoforms before and after N-deglycosylation with Peptide-N-Glycosidase F and tandem mass spectrometry sequencing of peptides obtained after Endoproteinase GluC digestion allowed the structural characterization of the peptide backbone and identification of N- and O-glycosylation sites. The heterogeneous mixture of the proteoforms derives from the combination of 8 different neutral and sialylated glycans O-linked to Threonine 50, and 33 different glycans N-linked to Asparagine residues at positions 66, 87, 108, 129, 150, 171, 192, and 213.