Lysine-cysteine NOS bonds

Lysine-cysteine "Nitrogen-Oxygen-Sulfur" (NOS) bonds () were first reported in 2021 in transaldolases^[1]. The sidechains of a lysine and a cysteine, joined by an NOS bond, make a covalent linkage between polypeptide chains. The disulfide bond is a far more common type of covalent linkage between polypeptide chains.

near the N-terminus of the 352 amino acid chain, between Lys8 and Cys38, near the surface.