In Brief Diversity in protein glycosylation can be described in terms of micro-heterogeneity and macro-heterogeneity, respectively, referring to the variation and occupancy of glycans at a given glycosylation site. However, these terms are not sufficient to describe a higher level of regulation when proteins are multiply glycosylated. For this, we propose the term meta-heterogeneity: variation in glycosylation across multiple sites of a given glycoprotein. In this review, we describe several remarkable examples of glycoprotein meta-heterogeneity and underline the need for its investigation.
