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Category: Bacterial Pathogenesis
The Dynamic Structures of the Type IV Pilus, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781683670285/9781683670278_Chap10-1.gif /docserver/preview/fulltext/10.1128/9781683670285/9781683670278_Chap10-2.gifAbstract:
The fundamental type IVa pilus (T4aP)-like architecture includes a retractable pilus fiber, a motor, an alignment subcomplex, and—in Gram-negative bacteria—an outer membrane secretin pore ( Fig. 1 ). The pilus is an extracellular polymer of pilins. Pilins subunits are stored in the inner membrane and the motor powers their polymerization (extension) and depolymerization (retraction) at the pilus base. The alignment subcomplex connects the secretin with the motor and controls pilus dynamics. Finally, the secretin pore allows the pilus to extend through the outer membrane. Since publication of previous T4aP reviews ( 1 – 4 ), discoveries made using cryo-electron microscopy (cryo-EM), cryo-electron tomography (cryo-ET), X-ray crystallography, and nuclear magnetic resonance (NMR) have dramatically reshaped our understanding of T4P-like systems. Here we put these discoveries in context with the structure and function of the T4aP, using the Pseudomonas aeruginosa T4aP system nomenclature.
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Subcomplexes of the T4aP. The protein structures portrayed reflect the full-length structure predictions and their predicted location in the T4aP. This figure is largely consistent with the previously published working model of the M. xanthus T4aP ( 43 ). Due to limited information, there is uncertainty regarding the locations of PilF, TsaP, PilY1, and the minor pilins.
The structures of the type IV pilus. The four subcomplexes are split into four quadrants, which are further subdivided into individual proteins in boxes colored to correspond to Fig. 1 . In the linear domain architecture, domains are displayed to scale as blocks colored to indicate known structures (rainbow colors), segments with high-confidence structure predictions (gray), unknown structures (white), transmembrane segments (diagonal bars), hydrolyzed signal peptides (black), or predicted/known disorder (black line). The known or predicted domain name is written; if a domain has no name, it could not be predicted. In the black outlined cartoon structures, a black outline of the predicted ( 127 – 129 ) full-length homology model is shown to scale for reference. Known structures are displayed as cartoons in rainbow colors corresponding to the colors shown in the linear domain architecture. A short description of the rainbow-colored cartoon structure and the PDB accession code are written in black font. Since the black outline is a P. aeruginosa structure prediction while the cartoons correspond to structures sometimes determined in other species, the black outline and cartoons may not fully match. Note that the PDB coordinate file for PilQ from T. thermophilus (marked with an asterisk) was obtained from the authors of reference 113 and used here with their permission; only the secretin and adjacent N1 domain (N5 in T. thermophilus) are shown here, as the other T. thermophilus PilQ domains are divergent or atypical compared to those in P. aeruginosa. (The N1 domain is also named N2, N3, N4, or N5 in systems or species where the N1 domain is duplicated.) No black outline is shown for FimV, as high-confidence structure prediction was not possible for most of this component. Unexpectedly, most of TsaP was predicted ( 127 ) with high confidence to be structurally similar to the protein with PDB code 3SLU. Gray boxes note interesting features of the protein or other relevant structures; structures in gray boxes are not to scale.
List of available T4aP structures a