The electrospray ionization (ESI)-tandem quadrupole/orthogonal-acceleration time-of-flight (Q-TOF) mass spectrometer combined with the nano-HPLC system was utilized to determine the glycosylation site and the glycan structure in glycoprotein TIME-EA4 (EA4) from Bombyx diapause eggs. LC-MS analysis of EA4 and deglycosylated EA4 indicated that the carbohydrate moiety of EA4 has the mass of 730.58 Da. Then, EA4 was digested with trypsin and chymotrypsin to identify the glycosylated peptide. The peptide fragment from G1y21 to Phe25 was found to carry the carbohydrate moiety. LC-MS/MS analysis of this peptide fragment revealed the sequence of the attached oligosaccharide and the glycosylation site at the same time. The present methodology utilizing the combination of the nano-HPLC system and a highly sensitive Q-TOF mass spectrometer is demonstrated to be quite effective for analyses of glycoproteins of relatively low purity and limited availability from natural sources.

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http://dx.doi.org/10.1016/s0968-0896(02)00040-8DOI Listing

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TIME-EA4 is an ATPase that measures time intervals, functioning as a diapause duration clock in diapause eggs of the silkworm, Bombyx mori. Characterization of the primary and higher structures of the TIME-EA4 would be desirable to clarify the mechanism by which the protein measures the time intervals. In our current studies, the whole sequence of TIME-EA4 has been established as that of a metallo-glycoprotein by combinational means involving peptide sequence analysis, nano-HPLC-ESI-Q-TOF-MS and MS/MS, and cDNA dictation.

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Structure of pentasaccharide of glycopeptide from TIME-EA4, N-glycoprotein in silkworm diapause eggs.

Bioorg Med Chem Lett

May 2004

Laboratory of Organic Chemistry, Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.

The TIME-EA4, from silkworm diapause eggs of pure strain C108, Bombyx mori, has glycosylated chain as tetrasaccharide (Man(2)GlcNAc(2)) attaching to the Asn(22) of T3 peptide from tryptic digests. On the other hand, from Showa silkworm strain we additionally observed a pentasaccharide (Man(3)GlcNAc(2)) on T3 at the same linkage site. The linkage pattern of the 5-sugar chain was studied through Smith degradation combined with LC-MS and MS/MS analyses.

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The electrospray ionization (ESI)-tandem quadrupole/orthogonal-acceleration time-of-flight (Q-TOF) mass spectrometer combined with the nano-HPLC system was utilized to determine the glycosylation site and the glycan structure in glycoprotein TIME-EA4 (EA4) from Bombyx diapause eggs. LC-MS analysis of EA4 and deglycosylated EA4 indicated that the carbohydrate moiety of EA4 has the mass of 730.58 Da.

View Article and Find Full Text PDF

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