Fig. 1. Schematic of the membrane dipeptidase (MDP) constructs used. Wild-type porcine MDP (wtMDP) contains an N-terminal 16 amino acid signal sequence (diagonally hatched box), two N-linked glycosylation sites (N41 and N263, lollipops) and a C-terminal GPI anchor addition signal (chequered box). The GPI anchor is attached to S368. In MDP
GPI and MDP
GPI
gly, A369 was mutated to a stop codon, resulting in secreted proteins. In MDP
gly and MDP
GPI
gly, N41 and N263 were mutated to Gln to prevent N-glycosylation.