FAQ: Is it possible to predict whether a protein is N- or O-glycosylated?

The oligosaccharyltransferase (OST) that links an N-glycan to an asparagine residue will recognize the minimal sequence Asn-X-Ser/Thr (where X is any residue except proline). There are several bioinformatic tools that factor the primary sequence, along with other structural features to determine the likelihood a given polypeptide will be substrate for glycosylation (for instance NetNGlyc). O-glycosylation on the other hand is more difficult to predict, since any exposed serine or threonine could be substrates for modification. Despite that, predictive tools have been developed (NetOGlyc) which are more or less accurate according to the nature of the protein analyzed.