title: Characterization of Anopheles gambiae transglutaminase 3 (AgTG3) and its native substrate Plugin.
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.
authors.affiliation: Department of Chemistry, Yale University, New Haven, Connecticut 06520-81070, USA.
authors.forename: Binh V
authors.initials: BV
authors.lastname: Le
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Nguyen
authors.forename: Shankar
authors.initials: S
authors.lastname: Logarajah
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.forename: Jacob
authors.initials: J
authors.lastname: Marcus
authors.forename: Hazel P
authors.initials: HP
authors.lastname: Williams
authors.forename: Flaminia
authors.initials: F
authors.lastname: Catteruccia
authors.forename: Richard H G
authors.initials: RH
authors.lastname: Baxter
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000201:enzymology*; D002118:Calcium / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D019281:Dimerization; D005260:Female; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D011503:Transglutaminases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D010455:Peptides; C000717608:TGM2 protein, human; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D002118:Calcium