Protein glycosylation, sweet to crystal growth?

In protein crystallization, post-translational modifications are often considered an annoyance. They are expected to introduce microheterogeneity into the protein and, in addition, in the case of the larger chemical modifications such as glycosylation, to increase surface entropy. On the one hand, these phenomena are said to be bad for crystal growth. On the other hand, many of these modifications are vital for proper folding and functioning of proteins. Over the past few years, we successfully crystallized several different glycoproteins, obtained by heterologous expression or directly isolated from their natural source. The crystallization of these proteins turned out to be fairly straightforward, and moreover, the carbohydrates were frequently found to be involved in forming (critical) intermolecular contacts. Opposite widespread opinions, an unbiased approach in crystallizing glycoproteins should prevail initially. Finally, several methodologies are listed that could be tried as a last resort.