A challenge faced by peptidases is the recognition of highly diverse substrates. A feature of some peptidase families is the capacity to specifically use post-translationally added glycans present on their protein substrates as a recognition determinant. This is ultimately critical to enabling peptide bond hydrolysis. This class of enzyme is also frequently large and architecturally sophisticated. However, the molecular details underpinning glycan recognition by these O-glycopeptidases, the importance of these interactions, and the functional roles of their ancillary domains remain unclear. Here, using the Clostridium perfringens ZmpA, ZmpB, and ZmpC M60 peptidases as model proteins, we provide structural and functional insight into how these intricate proteins recognize glycans as part of catalytic and noncatalytic substrate recognition. Structural, kinetic, and mutagenic analyses support the key role of glycan recognition within the M60 domain catalytic site, though they point to ZmpA as an apparently inactive enzyme. Wider examination of the Zmp domain content reveals noncatalytic carbohydrate binding as a feature of these proteins. The complete three-dimensional structure of ZmpB provides rare insight into the overall molecular organization of a highly multimodular enzyme and reveals how the interplay of individual domain function may influence biological activity. O-glycopeptidases frequently occur in host-adapted microbes that inhabit or attack mucus layers. Therefore, we anticipate that these results will be fundamental to informing more detailed models of how the glycoproteins that are abundant in mucus are destroyed as part of pathogenic processes or liberated as energy sources during normal commensal lifestyles.

No abstract

Protein glycosylation is ubiquitous throughout biology. From bacteria to humans, this post translational modification with sophisticated carbohydrate structures plays a profound role in the interaction of proteins with cells and changes the physiochemical properties of the proteins that carry them. When the glycans are linked to Ser or Thr residues they are known as O-linked glycans, as the glycosidic linkage is through oxygen. O-glycans are perhaps best known as part of the mucin proteins, however many soluble proteins carry these types of glycans, and that their roles in biology are still being discovered. Many of the soluble proteins that carry O-glycans have a role as therapeutic proteins, and in the 21st century, the application of synthetic biology is starting to be applied to improving these proteins through manipulation of the glycans. This review will explore the role of these O-linked glycans in proteins with pharmaceutical significance, as well as recent advancements in recombinant glycoprotein therapeutics.

No abstract

No abstract