Figure 2: Schematic presentation of the structure of human Plg. From the amino terminus of the mature protein, the 77-residue activation peptide (AP) is followed by 5 kringle domains (K1–K5) containing lysine binding sites and the catalytic SP domain. R561-V562, which is proteolytically cleaved to generate Pm, is shown with an asterisk. The cleavage site for plasminogen activator (PA) is shown by an arrow. Heavy chain and light chains after proteolytic cleavage are marked with lines.