We are honored to have a guest lecture on the next Microbiology Journal Club, organized by Friedman, Mills, and Levy labs. Please share the info with your students and colleagues. Prof. David Low
from the University of California at Santa Barbara will present the following talk on a bacterial toxin delivery system that his group discovered many years ago (CDI). "Contact-dependent growth inhibition: Insight into how toxin is delivered across the outer- and inner-membranes and activated in the cytosol"Abstract
: All bacteria must compete for growth niches and other limited environmental resources. These existential battles are waged at several levels, but one common strategy entails the transfer of growth-inhibitory protein toxins between competing cells. Contact-dependent growth inhibition (CDI) is the first touch-dependent toxin delivery system discovered (Science 309,1245; 2005), entailing receptor-mediated delivery of CdiA-derived toxins into Gram-negative target bacteria. Using electron cryotomography, we have shown that each CdiA effector protein forms a filament extending about 33 nm from the cell surface. Remarkably, the extracellular filament represents only the N-terminal half of the effector. A programmed secretion arrest sequesters the C-terminal half of CdiA, including the toxin domain, in the periplasm prior to target-cell recognition. Upon binding receptor, CdiA secretion resumes, and the periplasmic FHA-2 domain is transferred to the target-cell outer membrane. The C-terminal toxin region of CdiA then penetrates into the target-cell periplasm, where it is cleaved for subsequent translocation into the cytoplasm. The N-terminal domain appears to control toxin transport through specific inner membrane receptors. Notably, a number of CdiA toxins are not active when they gain entrance to the cytosol. Many CDI toxins that cleave tRNAs are inactive until they bind to the EF-Tu elongation factor. EF-Tu is the most abundant cellular protein, and binds tRNAs to deliver them to the ribosome. CDI tRNase toxins bind to EF-Tu and thus gain access to their tRNA targets, thereby depleting tRNAs and blocking protein synthesis.
Asaf Levy is inviting you to a scheduled Zoom meeting.
Topic: David Low - microbiology journal club
Time: Dec 10, 2020 09:00 AM Jerusalem
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Meeting ID: 847 1194 6691
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