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J. Biol. Chem., Vol. 277, Issue 30, 26846-26851, July 26, 2002

This Article Full Text Full Text (PDF) All Versions of this Article: 277/30/26846    most recent M202999200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gladysheva, I. P. Articles by Reed, G. L. Search for Related Content PubMed PubMed Citation Articles by Gladysheva, I. P. Articles by Reed, G. L. Social Bookmarking                      What's this?

Chimerism Reveals a Role for the Streptokinase -Domain in Nonproteolytic Active Site Formation, Substrate, and Inhibitor Interactions^*

Inna P. Gladysheva, Irina Y. Sazonova, Shakeel A. Chowdhry, Lin Liu, Ryan B. Turner, and Guy L. Reed

From the Cardiovascular Biology Laboratory, Harvard School of Public Health and the Massachusetts General Hospital, Boston, Massachusetts 02114

Streptokinase (SK) and staphylokinase form cofactor-enzyme complexes that promote the degradation of fibrin thrombi by activating human plasminogen. The unique abilities of streptokinase to nonproteolytically activate plasminogen or to alter the interactions of plasmin with substrates and inhibitors may be the result of high affinity binding mediated by the streptokinase -domain. To examine this hypothesis, a chimeric streptokinase, SKswap, was created by swapping the SK -domain with the homologous -domain of Streptococcus uberis Pg activator (SUPA or PauA, SK uberis), a streptokinase that cannot activate human plasminogen. SKswap formed a tight complex with microplasminogen with an affinity comparable with streptokinase. The SKswap-plasmin complex also activated human plasminogen with catalytic efficiencies (k_cat/K_m = 16.8 versus 15.2 µM¹ min¹) comparable with streptokinase. However, SKswap was incapable of nonproteolytic active site generation and activated plasminogen by a staphylokinase mechanism. When compared with streptokinase complexes, SKswap-plasmin and SKswap-microplasmin complexes had altered affinities for low molecular weight substrates. The SKswap-plasmin complex also was less resistant than the streptokinase-plasmin complex to inhibition by ₂-antiplasmin and was readily inhibited by soybean trypsin inhibitor. Thus, in addition to mediating high affinity binding to plasmin(ogen), the streptokinase -domain is required for nonproteolytic active site generation and specifically modulates the interactions of the complex with substrates and inhibitors.

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				I. Y. Sazonova, B. R. Robinson, I. P. Gladysheva, F. J. Castellino, and G. L. Reed {alpha} Domain Deletion Converts Streptokinase into a Fibrin-dependent Plasminogen Activator through Mechanisms Akin to Staphylokinase and Tissue Plasminogen Activator J. Biol. Chem., June 11, 2004; 279(24): 24994 - 25001. [Abstract] [Full Text] [PDF]

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