Forms hydroxylysine residues in -Xaa-Lys-Gly- sequences in collagens. These hydroxylysines serve as sites of attachment for carbohydrate units and are essential for the stability of the intermolecular collagen cross-links. 2-oxoglutarate + L-lysyl-[collagen] + O2 = (5R)-5-hydroxy-L-lysyl-[collagen] + CO2 + succinate Homodimer.