Summary: Pilin (bacterial filament)
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Pilin Edit Wikipedia article
|Pilin (bacterial filament)|
Pilin refers to a class of fibrous proteins that are found in pilus structures in bacteria. Bacterial pili are used in the exchange of genetic material during bacterial conjugation, and a short pilus called a fimbrium is used as a cell adhesion mechanism. Although not all bacteria have pili or fimbriae, bacterial pathogens often use their fimbriae to attach to host cells. In gram-negative bacteria, where pili are more common, individual pilin molecules are linked by noncovalent protein-protein interactions, while gram-positive bacteria often have polymerized pilin.
Pilin proteins themselves are α+β proteins characterized by a very long N-terminal alpha helix. Many pilins are post-translationally modified by glycosylation or phosphorylation. The assembly of a complete pilus relies on interactions between the N-terminal helices of the individual monomers. The pilus structure sequesters the helices in the center of the fiber lining a central pore, while antiparallel beta sheets occupy the exterior of the fiber. The exact mechanism of pilus assembly from monomers is not known, although chaperone proteins have been identified for some types of pilin. and specific amino acids required for proper pilus formation have been isolated.
Development of molecular tools
Pili in Gram-positive bacteria contain spontaneously formed isopeptide bonds. These bonds provide enhanced stability to the protein. Recently, the pilin protein from Streptococcus pyogenes has been split into two fragments to develop a new molecular tool called the isopeptag.  The isopeptag is a short peptide that can be attached to a protein of interest and can bind its binding partner through a spontaneously formed isopeptide bond. This new peptide tag can allow scientists to target and isolate their proteins of interest through a permanent covalent bond.
- ^ Telford JL, Barocchi MA, Margarit I, Rappuoli R, Grandi G. (2006). Pili in gram-positive pathogens. Nat Rev Microbiol 4(7):509-19.
- ^ Forest KT, Tainer JA. (1997). Type-4 pilus-structure: outside to inside and top to bottom--a minireview. Gene 192(1):165-9.
- ^ Jones CH, Pinkner JS, Nicholes AV, Slonim LN, Abraham SN, Hultgren SJ. (1993). FimC is a periplasmic PapD-like chaperone that directs assembly of type 1 pili in bacteria. Proc Natl Acad Sci USA 90(18):8397-401.
- ^ Mu XQ, Jiang ZG, Bullitt E. (2005). Localization of a critical interface for helical rod formation of bacterial adhesion P-pili. J Mol Biol 346(1):13-20.
-  Zakeri,B. and Howarth,M. (2010). Spontaneous intermolecular amide bond formation between side chains for irreversible peptide targeting. J. Am. Chem. Soc. 132, 4526-4527.
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Proteins with only the short N-terminal methylation site are not separated from the noise. The Prosite pattern detects those better.
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001082Pilin is a subunit of the pilus, a polar flexible filament, which consists of a single polypeptide chain arranged in a helical configuration of five subunits per turn. Gram-negative bacteria produce pilin which is characterised by the presence of a very short leader peptide of 6 to 7 residues, followed by a methylated N-terminal phenylalanine residue and by a highly conserved sequence of about 24 hydrophobic residues, of the NMePhe type pilin [PUBMED:2898203, PUBMED:3118043].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||pilus (GO:0009289)|
|Biological process||cell adhesion (GO:0007155)|
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Curation and family details
|Number in seed:||147|
|Number in full:||1425|
|Average length of the domain:||110.70 aa|
|Average identity of full alignment:||23 %|
|Average coverage of the sequence by the domain:||71.92 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||14|
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There is 1 interaction for this family. More...
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Pilin domain has been found. There are 48 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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