P pilus

Bacterial pili appear to be extruded in a similar manner. They arise rapidly and may possibly be retracted again into the bacterial membrane. The P pilus in Fig. 7-9A is made up of subunits Pap A, G, F,... 

Knutton, S., Shaw, R. K., Anantha, R. P., Donnenberg, M. S., and Zorgani, A. A. (1999). The type rV bundle-forming pilus of enteropathogenic Escherichia coli undergoes dramatic alterations in structure associated with bacterial adherence, aggregation and dispersal. 

Srimanote, P., Paton, A. W., and Paton, J. C. (2002). Characterization of a novel type IV pilus locus encoded on the large plasmid of locus of enterocyte effacement-negative Shiga-toxigenic Escherichia coli strains that are virulent for humans. Infect. Immun. 70,3094-3100. 

Freeze-etch electron microscopy of P pili revealed that they are composite fibers consisting of two distinct structures (Kuehn et ai, 1992) (see later. Fig. 8). The stalk of the pilus is composed of repeating monomers... 

The production of adhesive P pili requires PapC, which is an 88-kDa outer membrane protein. Genetic lesions in PapC result in a block in the assembly pathway, leading to an accumulation of chaperone-pilus protein complexes in the periplasm (Norgren et al., 1987). Thus, in the absence of PapC it seems that the chaperone preassembly complexes are no longer targeted to outer membrane assembly sites. As a consequence, the periplasmic chaperone remains bound to the subunits, preventing their assembly into pili. 

An example of a study of the dynamic response that follows a sudden halt in elongation is shown in Fig. 18.7b together with fits to (18.8), and it reveals that the force for P and type 1 pili relaxes to the steady-state force according to (18.8) for both types of pilus, although with significantly dissimilar speeds for the two types of pilus. 

Table 18.1 presents a compilation of some bond parameters that have been assessed for P and type 1 pili. Parameters for other t3cpes of pilus, e.g., S and FlC, which are presently under scrutiny, will be presented elsewhere. In addition to measurements on P and t3cpe 1 pili performed by the authors [12,14-18,21,36,37], the table includes some parameters for t3cpe 1 pili assessed by Miller et al. [50] and Forero et al. [51] using force measuring AFM. Note though, to make a comparison possible with the results obtained by the OT-technique, some of their values have been recalculated to agree with the nomenclature used with OT. 

Merz, A.J., So, M. and Sheetz, M.P. (2000). Pilus retraction powers bacterial twitching motility. Nature 407, 98-102. 

Figure 9. Model of motility mediated by the type IV pilus. Reproduced from Current Biology, Vol. 10, Sun et at, Type IV pilus of Myxococcus xanthus is a motility apparatus controlled by the frz chemosensory system, p. 1146, 2000 [118], with pei mission from the author and from Elsevier Science.

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