Blomfield, I.C. (2001) The regulation of pap and type 1 fimbriation in Escherichia coli. Adv Microb Physiol, 45 (1-49). pp. 1-49. ISSN 0065-2911 .
|The full text of this publication is not available from this repository. (Contact us about this Publication)|
The ability of bacterial pathogens to bind to the host mucosa is a critical step in the pathogenesis of many bacterial infections and, for Escherichia coli, a large number of different fimbrial adhesins have been implicated as virulence factors. In this chapter, our current understanding of the regulatory mechanisms that control the expression of two of the best characterized fimbrial adhesins, pyelonephritis-associated pilus (encoded by pap) and the type 1 fimbria (encoded by fim), will be described. The expression of both fimbrial adhesins is controlled by phase variation (the reversible and apparently random switching between expressing ('on') and non-expressing ('off') states), and is regulated in response to environmental conditions. The phase variation of pap (and of some other fimbriae in Escherichia coli) is determined by the formation of alternative nucleoprotein complexes that either activate (phase 'on') or suppress (phase 'off') transcription of the fimbria genes. Formation of each complex protects a single Dam methylation site (5' GATC) from modification (GATCdist in phase 'on' cells and GATCprox in phase 'off' cells). Furthermore, complex formation is inhibited by methylation of the two 5' GATC sites. Both the phase variation of pap and the transcription of the pap genes in phase 'on' cells, are regulated and expression is subject to both positive and negative feedback control. In contrast to pap, the phase variation of fim is determined by the site-specific inversion of a short element of DNA (the fim switch). In phase 'on' cells, a promoter within the invertible element directs the transcription of the fim structural genes, whereas in phase 'off' cells transcription of the fimbrial genes is silenced. Despite the very different molecular mechanisms controlling the expression of pap and fim, the two systems share many features in common and have probably evolved to fulfill the same function. In addition to details about the molecular mechanisms that control pap and fim, the possible physiological significance of the observed regulation will be discussed.
|Additional information:||0065-2911 (Print) Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Review|
|Uncontrolled keywords:||Adhesins, Escherichia coli/chemistry/genetics/*physiology Amino Acid Sequence Escherichia coli/chemistry/genetics/*physiology Feedback Fimbriae, Bacterial/chemistry/genetics/*physiology Gene Expression Regulation, Bacterial/*physiology Methylation Molecular Sequence Data Sequence Alignment Sequence Homology, Amino Acid|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||Sue Davies|
|Date Deposited:||30 Sep 2009 15:34|
|Last Modified:||30 Sep 2009 15:34|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/22673 (The current URI for this page, for reference purposes)|
- Depositors only (login required):