Fig. 2.

Clustered Tenebrio PGRP-SA is required for prophenoloxidase activation. (A) Lys-type PG-dependent phenoloxidase activity was measured with 10 nM Tenebrio PGRP-SA (0.2 μg·ml⁻¹) and different amounts of the linearized PG (squares). The bell-shaped dose–response curve was shifted to the right by the addition of Tenebrio PGRP-SA to 120 nM (2.5 μg·ml⁻¹), and a maximal point was observed at 100 ng of the linearized PG (circles). Insets indicate the putative initial complexed structures between Tenebrio PGRP-SA and the linearized PG. R and PG indicate Tenebrio PGRP-SA and linearized Lys-type PG, respectively. (B) In vitro reconstitution experiments were performed by using Tenebrio PGRP-SA or Drosophila PGRP-SA with the Tenebrio PGRP-SA-deficient hemolymph solution in the presence of the linearized PG (columns 2 and 3, respectively). Tenebrio PGRP-SA and Drosophila PGRP-SA were coincubated in the presence of the linearized PG (column 4).