Probably plays a role in the assembly of the spore coat proteins by catalyzing epsilon-(gamma-glutamyl)lysine cross-links. In wild-type spores at 37 degrees Celsius, tgl mediates the cross-linking of GerQ in higher molecular mass forms, probably in cooperation with YabG. L-glutaminyl-[protein] + L-lysyl-[protein] = [protein]-L-lysyl-N(6)-5-L-glutamyl-[protein] + NH4(+) Expressed during sporulation. In cells missing this gene some GerQ multimers are present, indicating that tgl is not essential. Heat treatment for 20 minutes at 60 degrees Celsius, which maximally activates the Tgl enzymatic activity, causes cross-linking of GerQ in isolated yabG-deleted spores but not in tgl/yabG double-mutant spores. Additionally, the germination frequency of the tgl/yabG double-mutant spores in the presence of L-alanine with or without heat activation at 60 degrees Celsius is lower than that of wild-type spores. Belongs to the bacillus TGase family.