Mechanism of cooperative N-glycan processing by the multi-modular endoglycosidase EndoE
Mikel García-Alija, Jonathan J. Du, Izaskun Ordóñez, Asier Diz-Vallenilla, Alicia Moraleda-Montoya, Nazneen Sultana, Chau G. Huynh, Chao Li, Thomas C. Donahue, Lai‐Xi Wang, Beatriz Trastoy, Eric J. Sundberg, Marcelo E. Guerin
Abstract
Bacteria produce a remarkably diverse range of glycoside hydrolases to metabolize glycans from the environment as a primary source of nutrients, and to promote the colonization and infection of a host. Here we focus on EndoE, a multi-modular glycoside hydrolase secreted by Enterococcus faecalis, one of the leading causes of healthcare-associated infections. We provide X-ray crystal structures of EndoE, which show an architecture composed of four domains, including GH18 and GH20 glycoside hydrolases connected by two consecutive three α-helical bundles. We determine that the GH20 domain is an exo-β-1,2-N-acetylglucosaminidase, whereas the GH18 domain is an endo-β-1,4-N-acetylglucosaminidase that exclusively processes the central core of complex-type or high-mannose-type N-glycans. Both glycoside hydrolase domains act in a concerted manner to process diverse N-glycans on glycoproteins, including therapeutic IgG antibodies. EndoE combines two enzyme domains with distinct functions and glycan specificities to play a dual role in glycan metabolism and immune evasion.