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Schlagwörter:
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Zusammenfassung:
Many pathogenic bacteria use the type III secretion system (T3SS), or
injectisome, to secrete toxins into host cells. These protruding systems
are primary targets for drug and vaccine development. Upon contact
between injectisomes and host membranes, toxin secretion is triggered.
How this works structurally and functionally is yet unknown. Using
cryo-focused ion beam milling and cryo-electron tomography, we
visualized injectisomes of Yersinia enterocolitica inside the phagosomes
of infected human myeloid cells in a close-to-native state. We observed
that a minimum needle length is required for injectisomes to contact the
host membrane and bending of host membranes by some injectisomes that
contact the host. Through subtomogram averaging, the structure of the
entire injectisome was determined, which revealed structural differences
in the cytosolic sorting platform compared to other bacteria. These
findings contribute to understanding how injectisomes secrete toxins
into host cells and provides the indispensable native context. The
application of these cryo-electron microscopy techniques paves the way
for the study of the 3D structure of infection-relevant protein
complexes in host-pathogen interactions.
