2ffu

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spinqualitylabelsall models 2ffu, resolution 1.64Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure of Human ppGalNAcT-2 complexed with UDP and EA2

Overview

The family of UDP-GalNAc:polypeptide, alpha-N-acetylgalactosaminyltransferases (ppGalNAcTs) is unique among, glycosyltransferases, containing both catalytic and lectin domains that we, have previously shown to be closely associated. Here we describe the x-ray, crystal structures of human ppGalNAcT-2 (hT2) bound to the product UDP at, 2.75 A resolution and to UDP and an acceptor peptide substrate EA2, (PTTDSTTPAPTTK) at 1.64 A resolution. The conformations of both UDP and, residues Arg362-Ser372 vary greatly between the two structures. In the, hT2-UDP-EA2 complex, residues Arg362-Ser373 comprise a loop that forms a, lid over UDP, sealing it in the active site, whereas in the hT2-UDP, complex this loop is folded back, exposing UDP to bulk solvent. EA2 binds, in a shallow groove with threonine 7 positioned consistent with in vitro, data showing it to be the preferred site of glycosylation. The relative, orientations of the hT2 catalytic and lectin domains differ dramatically, from that of murine ppGalNAcT-1 and also vary considerably between the two, hT2 complexes. Indeed, in the hT2-UDP-EA2 complex essentially no contact, is made between the catalytic and lectin domains except for the peptide, bridge between them. Thus, the hT2 structures reveal an unexpected, flexibility between the catalytic and lectin domains and suggest a new, mechanism used by hT2 to capture glycosylated substrates. Kinetic analysis, of hT2 lacking the lectin domain confirmed the importance of this domain, in acting on glycopeptide but not peptide substrates. The structure of the, hT2-UDP-EA2 complex also resolves long standing questions regarding, ppGalNAcT acceptor substrate specificity.

About this Structure

2FFU is a Protein complex structure of sequences from Homo sapiens with MN and UDP as ligands. Active as Polypeptide N-acetylgalactosaminyltransferase, with EC number 2.4.1.41 Full crystallographic information is available from OCA.

Reference

Dynamic association between the catalytic and lectin domains of human UDP-GalNAc:polypeptide alpha-N-acetylgalactosaminyltransferase-2., Fritz TA, Raman J, Tabak LA, J Biol Chem. 2006 Mar 31;281(13):8613-9. Epub 2006 Jan 24. PMID:16434399

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