Structural and Inhibitory Effects of Hinge Loop Mutagenesis in Serpin-2 from the Malaria Vector Anopheles gambiae.

摘要: Serpin-2 (SRPN2) is a key negative regulator of the melanization response in malaria vector Anopheles gambiae. SRPN2 irreversibly inhibits clip domain serine proteinase 9 (CLIPB9), which functions cascade culminating activation prophenoloxidase and melanization. Silencing A. gambiae results spontaneous decreased life span therefore promising target for control. The previously determined structure revealed partial insertion hinge region reactive center loop (RCL) into β sheet This participates heparin-linked other serpins, notably antithrombin III. does not contain heparin binding site, any possible mechanistic function was unknown. To investigate insertion, we developed three variants regions are either constitutively expelled or inserted analyzed their structure, thermostability, inhibitory activity. We that constitutive expulsion resulted 2.7-fold increase rate CLIPB9Xa inhibition, significantly lower than previous observations allosteric serpin activation. Furthermore, stable did appreciably decrease accessibility RCL to CLIPB9. Together, these indicate participate observed serpins instead represents molecular trade-off between efficient formation an complex with cognate proteinase.