The Ribosome Is the Ultimate Receptor for Trypsin Modulating Oostatic Factor (TMOF).

Aedes aegypti Trypsin Modulating Oostatic Factor ( Aea TMOF). a mosquito decapeptide that controls trypsin biosynthesis in female and larval mosquitoes. enters the gut epithelial cells of female mosquitoes using ABC- tmf A receptor/importer. To study the ultimate targeted receptor after Aea TMOF enters the cell, Aea TMOF was incubated in vitro with either Escherichia coli or Spodoptera frugiperda protein-expressing extracts containing 70S and 80S ribosomes, respectively. The effect of Aea TMOF on luciferase biosynthesis in vitro using 70S ribosomes was compared with that of oncocin112 (1-13), a ribosome-binding antibacterial peptide. The IC 50 of 1 μM and 2 μM, respectively, for both peptides was determined. Incubation with a protein-expressing system and S. frugiperda 80S ribosomes determined an IC 50 of 1.8 μM for Aedes aegypti larval late trypsin biosynthesis. Incubation of purified E. coli ribosome with increasing concentration of Aea TMOF shows that the binding of Aea TMOF to the bacterial ribosome exhibits a high affinity (K D = 23 ± 3.4 nM, B max = 0.553 ± 0.023 pmol/μg ribosome and K assoc = 4.3 × 10 7 M -1 ). Molecular modeling and docking experiments show that Aea TMOF binds bacterial and Drosophila ribosome (50S and 60S, respectively) at the entrance of the ribosome exit tunnel, blocking the tRNA entrance and preventing protein biosynthesis. Recombinant E. coli cells that express only ABC- tmf A importer are inhibited by Aea TMOF but not by oncocin112 (1-13). These results suggest that the ribosome is the ultimate targeted receptor of Aea TMOF.