Crystals of SctV from different species reveal variable symmetry for the cytosolic domain of the type III secretion system export gate

Type III secretion systems (T3SSs) are proteinaceous devices employed by Gram-negative bacteria to directly transport proteins into a host cell. Substrate recognition and secretion are strictly regulated by the export apparatus of the so-called injectisome. The export gate SctV engages chaperone-bound substrates of the T3SS in its nonameric cytoplasmic domain. Here, the purification and crystallization of the cytoplasmic domains of SctV from Photorhabdus luminescens (LscVC) and Aeromonas hydrophila (AscVC) are reported. Self-rotation functions revealed that LscVC forms oligomers with either eightfold or ninefold symmetry in two different crystal forms. Similarly, AscVC was found to exhibit tenfold rotational symmetry. These are the first instances of SctV proteins forming non-nonameric oligomers.

Source: Acta Crystallographica Section F - October 14, 2022 Category: Biochemistry Authors: Gilzer, D. Baum, E. Lieske, N. Kowal, J.L. Niemann, H.H. Tags: type III secretion systems export-gate protein SctV Photorhabdus luminescens Aeromonas hydrophila cyclic oligomers low-resolution crystallography molecular replacement oligomerization self-rotation function research communications Source Type: research