Pilus-like structure

The elongation of a linearized pilus, i.e., when the entire helix-like structure has been unfolded and the pilus resides in region III, differs from that of a helix-like structure in the respect that all bonds have the same probability to... 

The three-dimensional structure of the PapD periplasmic chaperone that forms transient complexes with pilus subunit proteins has been solved by Holmgren and Branden (1989). PapD consists of two globular domains oriented in the shape of a boomerang (Fig. 2). Each domain is a /3-barrel structure formed by two antiparallel /8-pleated sheets that have a topology similar to an immunoglobulin fold. The relationship between PapD and other immunoglobulin-like proteins is discussed in Section IV,C. 

Due to its structure, a pilus has an intricate force response that differs from that of a single bond as well as those of many other types of biopolymer. As illustrated in Fig. 18.2b, a force-vs.-elongation response of a single pilus can be seen as composed of three regions Region /, in which the response is basically linear, like that of a normal (elastic) spring Region II, in which the... 

Various pathogenic bacteria inject proteins into host cells via a complicated syringe-like machine composed of more than 20 different proteins. This type III secretion apparatus, shown in Figure 16-24, has ringlike components embedded in both the inner and outer membranes of the bacterial cell wall and a hollow needlelike structure (pilus) that projects... 

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