Work

Characterization of Anopheles gambiae Transglutaminase 3 (AgTG3) and Its Native Substrate Plugin

Year: 2013

Type: article

Abstract: Male Anopheles mosquitoes coagulate their seminal fluids via cross-linking of a substrate, called Plugin, by the seminal transglutaminase AgTG3. Formation of the "mating plug" by cross-linking Plugin is necessary for efficient sperm storage by females. AgTG3 has a similar degree of sequence identity (∼30%) to both human Factor XIII (FXIII) and tissue transglutaminase 2 (hTG2). Here we report the solution structure and in vitro activity for the cross-linking reaction of AgTG3 and Plugin. AgTG3 is a dimer in solution and exhibits Ca 2+ -dependent nonproteolytic activation analogous to cytoplasmic FXIII. The C-terminal domain of Plugin is predominantly α-helical with extended tertiary structure and oligomerizes in solution. The specific activity of AgTG3 was measured as 4.25 × 10 −2 units mg −1 . AgTG3 is less active than hTG2 assayed using the general substrate TVQQEL but has 8–10× higher relative activity when Plugin is the substrate. Mass spectrometric analysis of cross-linked Plugin detects specific peptides including a predicted consensus motif for cross-linking by AgTG3. These results support the development of AgTG3 inhibitors as specific and effective chemosterilants for A. gambiae . Background: A. gambiae transglutaminase AgTG3 cross-links Plugin within seminal fluids. Results: AgTG3 and Plugin were purified and their structure and activity characterized in vitro . Conclusion: AgTG3 forms a dimer in solution, analogous to human FXIII. Plugin is nonglobular in solution. AgTG3 is Ca 2+ -dependent and prefers Plugin as a substrate. Significance: Inhibition of AgTG3 cross-linking of Plugin is a possible method to chemosterilize male Anopheles mosquitoes.

Source: Journal of Biological Chemistry

DOI: 10.1074/jbc.m112.435347