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A pilus (Latin for 'hair'; pl.: pili) is a hair-like cell-surface appendage found on many bacteria and archaea. [1] The terms pilus and fimbria (Latin for 'fringe'; plural: fimbriae ) can be used interchangeably, although some researchers reserve the term pilus for the appendage required for bacterial conjugation .
LPXTG Pili in Gram-positive bacteria contain spontaneously formed isopeptide bonds. These bonds provide enhanced mechanical [12] and proteolytic [13] stability to the pilin protein. Recently, the pilin protein from Streptococcus pyogenes has been split into two fragments to develop a new molecular tool called the isopeptag. [14]
Type IV secretion systems are a highly versatile group, present in Gram positive bacteria, Gram negative bacteria, and archaea. They usually involve a single step which utilizes a pilus, though exceptions exist. [3] Type IV secretion systems are highly diverse, with a variety of functions and types due to different evolutionary paths.
The F-pili are extremely resistant to mechanical and thermochemical stress, which guarantees successful conjugation in a variety of environments. [10] Several proteins coded for in the tra or trb locus seem to open a channel between the bacteria and it is thought that the traD enzyme, located at the base of the pilus, initiates membrane fusion.
Lipid II is a precursor molecule in the synthesis of the cell wall of bacteria. It is a peptidoglycan, which is amphipathic and named for its bactoprenol hydrocarbon chain, which acts as a lipid anchor, embedding itself in the bacterial cell membrane. Lipid II must translocate across the cell membrane to deliver and incorporate its disaccharide ...
Transfer genes or tra genes (also transfer operons or tra operons), are some genes necessary for non-sexual transfer of genetic material in both gram-positive and gram-negative bacteria. The tra locus includes the pilin gene and regulatory genes, which together form pili on the cell surface, polymeric proteins that can attach themselves to the ...
The pili are a pivotal virulence factor for N. gonorrhoeae; without them, the bacterium is unable to promote colonization. [48] For motility, individual bacteria use their pili in a manner that resembles a grappling hook: first, they are extended from the cell surface and attach to a substrate. Subsequent pilus retraction drags the cell forward.
Sortase refers to a group of prokaryotic enzymes that modify surface proteins by recognizing and cleaving a carboxyl-terminal sorting signal.For most substrates of sortase enzymes, the recognition signal consists of the motif LPXTG (Leu-Pro-any-Thr-Gly), then a highly hydrophobic transmembrane sequence, followed by a cluster of basic residues such as arginine.