Luminescent bacterial symbionts of nematode worms that attack insects have long stirred interest in their possibilities for biological control. The bacteria produce a family of toxins composed of at least three subunits that resemble a widely occurring class of bacterial toxins also produced by human pathogens. Lang et al. have elucidated the mode of action and structural interactions of some of these tripartite protein toxins and found that they poison the cell’s actin cytoskeleton by catalyzing unusual reactions. One toxin mediated adenosine diphosphate (ADP) ribosylation at threonine-148 to cause actin polymerization, another ADP-ribosylated Rho protein at glutamine-63, and both synergized to cause actin clustering and cell paralysis.
A. E. Lang, G. Schmidt, A. Schlosser, T. D. Hey, I. M. Larrinua, J. J. Sheets, H. G. Mannherz, K. Aktories, Photorhabdus luminescens toxins ADP-ribosylate actin and RhoA to force actin clustering. Science 327, 1139–1142 (2010). [Abstract] [Full Text]