Structural basis for N-glycopeptide preference in an infant-derived Bifidobacterium bifidum PNGaseA.

An infant-derived Bifidobacterium bifidum LMG13195 PNGaseA-family enzyme preferentially acts on N-glycans on glycopeptides, with structures revealing cradle-loop closure over the peptide C terminus.

• Why it matters: Breast milk contains many N-glycosylated proteins that infant gut microbes can access, but how PNGaseA enzymes recognize glycopeptides versus proteins is unclear.
• What they did: The team biochemically and structurally characterized the PNGaseA-family enzyme using apo, an E236Q mutant, and a D107N-E236Q complex with a G2-peptide, plus molecular dynamics and mutational analyses.
• The result: Glycopeptide binding is linked to β-sheet cradle-loop movements that close against β-sandwich 1, positioning the scissile amide and concentrating peptide contacts around the +2 Thr residue of the NXT sequon.

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