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where is the MS data supporting this work?

Posted by MarioFeldman on 20 Dec 2012 at 07:38 GMT

The authors use the same lectin to identify and validate what they claim to be glycoproteins in E. coli. No structures for the sugars or glycosylation mechanisms are deascribed. This work does not show conclusive evidence for the presence of glycoproteins in E. coli.

No competing interests declared.

RE: where is the MS data supporting this work?

chipschips302 replied to MarioFeldman on 22 Jan 2013 at 06:29 GMT

Thanks for the comments and your interest in our work. The aim of this work is to identify prokaryotic glycoproteins in a systematical way. By using an E.coli proteome microarray with >4,000 proteins, we successfully identified >20 possible glycoproteins, these proteins could serve as a valuable start point for follow-up functional studies. Indeed, the most accurate way to confirm a protein is glycosylated could be mass spectrometry analysis. Theoretically, both the glycosylation site/sites and the glycan structure could be obtained by MS analysis. However, the accessibility of this analysis is very limited because of the expensive instruments and the technical difficulties. Thus, we chose lectin blotting to validate the candidate glycoproteins. As shown by numerous studies, lectin blotting is a well established assay for confirming the glycosylation status of a glycoprotein. Because of the specific binding of lectin to glycans, it is no doubt that the positive signal of lectin blotting could serve as conclusive evidence that the protein tested is glycosylated, though we still do not know the glycosylation site/sites on the protein and the glycan structure. Again, thanks for your comments.

No competing interests declared.

RE: RE: where is the MS data supporting this work?

MarioFeldman replied to chipschips302 on 11 Mar 2013 at 22:22 GMT

Thank you for your response, unfortunately I still believe that your work does not demonstrate the presence of glycoproteins in Escherichia coli at all. We ( and others, you can read Warren Wakarchuk's comments) have used lectins in the past and we are positive that they bind to unglycosylated proteins in an unspecific manner. MS is not that expensive. You should try to confirm glycosylation via MS for at least one of your proteins. Until then, we and many others remain skeptical of of the validity of your approach and conclusions.

No competing interests declared.