The kringle 4 domain of chicken plasminogen

The kringle 4 unit of chicken plasminogen is similar to mammalian kringle 4 domains in possessing a lysine-binding site. Chicken kringle 4 shows 73-77% sequence identity with the fourth kringle units of porcine, bovine and human plasminogens. A major difference between mammalian and chicken kringle 4 species is that in the latter a glucosamine-based carbohydrate substituent is linked to asparagine-34. Complexation of this carbohydrate with concanavalin A does not interfere with the binding of kringle 4 to lysine-Sepharose, suggesting that in the kringle-fold the glycosylated region is distant from the entrance of the lysine-binding pocket.