Proximity of the catalytic region and the kringle 2 domain in the closed conformer of plasminogen.

Introduction of a single intramolecular cross-link with 1,5-difluoro-2,4-dinitrobenzene into Glu-plasminogen freezes the molecule in its closed conformational state (Bányai, L. and Patthy, L. (1984) J. Biol. Chem. 259, 6466-6471). Here we show that the cross-link connects Lys-203 of the kringle 2 domain and Tyr-671 of the catalytic domain, indicating that these regions are in close proximity in the closed conformer of Glu-plasminogen. Comparison of the parameters of the urokinase-catalysed activation of native and cross-linked Glu-plasminogen species indicates that cross-linking of kringle 2 and the catalytic region interferes with the productive binding of urokinase to plasminogen.