Research press release


Nature Structural & Molecular Biology

Seeing a bacterial needle in action



Thomas Marlovitsたちは構造生物学と画像化技術を用い、サルモネラのT3SSが病原因子を宿主細胞内に送り込む仕組みを示した。 Marlovitsたちは、操作した基質分子を結合しているインジェクチソームの三次元モデルを作り、基質を分泌している過程にあるT3SS装置全体を描き出すことに成功した。Marlovitsたちは、インジェクチソーム複合体の中央にある「穴」を基質分子が通り抜けることを明らかにし、宿主細胞へと通り抜けるために病原因子がまず折りたたみをほどくに違いないことを示している。


The path by which pathogenic bacteria inject toxic molecules into host cells is visualized for the first time in a study published online this week in Nature Structural & Molecular Biology.

Type-3 secretion systems (T3SSs) are highly-conserved protein machineries that inject bacterial toxic molecules, known as virulence factors, directly into host cells, thereby modulating the host cell’s functions. Central to T3SSs is the injectisome, a syringe-like needle complex anchored in the bacterium that is believed to provide a path for the virulence factors to enter targeted cells.

Thomas Marlovits and colleagues used structural biology and imaging techniques to show how Salmonella T3SS transfers virulence factors into host cells. They were able to create a three-dimensional model of the injectisome with an engineered substrate molecule and then visualize the entire T3SS apparatus in the process of secreting substrate. Marlovits and colleagues found substrate molecules passing through the central “bore” of the injectisome complex, indicating that virulence factors must first unfold in order to be passed through to the host cell.

As T3SSs are essential to the virulence of a variety of pathogenic bacteria, blocking the pathway to host-cell entry via T3SSs may be a promising therapeutic approach to battle bacterial infections.

doi: 10.1038/nsmb.2722


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