Dynamic interplay between catalytic and lectin domains of GalNAc-transferases modulates protein O-glycosylation

Erandi Lira-Navarrete, Matilde de las Rivas, Ismael Compañón, María Carmen Pallarés, Yun Kong, Javier Iglesias-Fernández, Gonçalo J. L. Bernardes, Jesús M. Peregrina, Carme Rovira, Pau Bernadó, Pierpaolo Bruscolini, Henrik Clausen, Anabel Lostao, Francisco Corzana & Ramon Hurtado-Guerrero. Nature Communications 6, Article number: 6937 doi:10.1038/ncomms7937

Protein O-glycosylation is controlled by polypeptide GalNAc-transferases (GalNAc-Ts) that uniquely feature both a catalytic and lectin domain. The underlying molecular basis of how the lectin domains of GalNAc-Ts contribute to glycopeptide specificity and catalysis remains unclear. Here we present the first crystal structures of complexes of GalNAc-T2 with glycopeptides that together with enhanced sampling molecular dynamics simulations demonstrate a cooperative mechanism by which the lectin domain enables free acceptor sites binding of glycopeptides into the catalytic domain. Atomic force microscopy and small-angle X-ray scattering experiments further reveal a dynamic conformational landscape of GalNAc-T2 and a prominent role of compact structures that are both required for efficient catalysis. Our model indicates that the activity profile of GalNAc-T2 is dictated by conformational heterogeneity and relies on a flexible linker located between the catalytic and the lectin domains. Our results also shed light on how GalNAc-Ts generate dense decoration of proteins with O-glycans.

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