Linked Life Data

1683764

Source:http://linkedlifedata.com/resource/pubmed/id/1683764

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
1992-1-6
pubmed:abstractText
The assembly of bacterial pili as exemplified here by P and type 1 pili of E. coli is a complex process involving specific molecular interactions between structural and chaperone proteins. The assembly process occurs postsecretionally, i.e. after the subunits are translocated across the cytoplasmic membrane. In a single cell, hundreds of thousands of interactive subunits are typically surface localized and assembled into pili. Periplasmic chaperones are generally required to bind to the interactive subunits and partition them into assembly-competent complexes. The binding of the chaperone to the subunits apparently protects the interactive surfaces and prevents them from aggregating at the wrong time and place within the cell. Pili are most likely assembled into linear polymers that package into right-handed helices after their translocation through specific outer-membrane channels. Each pilus filament is a quaternary assembly of the structural subunit and several minor subunits including the adhesin moiety. Although the assembly and organization of P and type 1 pili are very similar, there are some notable differences. For example, the P pilus adhesin is located exclusively at the tips of the pilus filament and forms part of a morphologically distinct structure. In contrast, the adhesion moiety of type 1 pili is inserted into the pilus filament at intervals, but only the adhesin molecule exposed at the pilus tip is functional. The variability in isoreceptor recognition amongst P pili has been solely ascribed to structural differences in the respective adhesin molecules, whereas in type 1 pili, variability in binding specificity has been attributed to the pilus filament that influences the conformation of the adhesin moiety. Less is known about the structure or assembly of type 4 pili, which are a unique class of pili expressed by several different species of gram-negative bacteria. The phase variation of the pilC assembly gene in N. gonorrheae to the off state results in the accumulation of unassembled subunits toxic to the cells. This process exerts a strong selection pressure on the cells that triggers alterations in the pilin structural gene. Thus, antigenic variation of pili in this organism may be regulated at the level of assembly. Finally, the concept of periplasmic chaperones in postsecretional assembly is most likely a general phenomenon in the biology of gram-negative bacteria. The investigations of pilus assembly will continue to provide insight into the details of how macromolecular assembly reactions are coordinated in the bacterial cell and how the regulation of assembly genes can profoundly affect biological processes.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0066-4227
pubmed:author
pubmed:issnType
Print
pubmed:volume
45
pubmed:geneSymbol
fim, pap, pil, prs
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
383-415
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Chaperone-assisted assembly and molecular architecture of adhesive pili.
pubmed:affiliation
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S., Review, Research Support, Non-U.S. Gov't