Rhs elements of Escherichia coli: a family of genetic composites each encoding a large mosaic protein

Mol Microbiol. 1994 Jun;12(6):865-71. doi: 10.1111/j.1365-2958.1994.tb01074.x.

Abstract

The Rhs family comprises a set of composite elements found in the chromosomes of many natural Escherichia coli strains. Five Rhs elements occur in strain K-12. The most prominent Rhs component is a giant core open reading frame (core ORF) whose features are suggestive of a cell surface ligand-binding protein. This hypothetical protein contains a peptide motif, xxGxxxRYxYDxxGRL(I or T)xxxx, that is repeated 28 times. A similar repeated motif is found in a Bacillus subtilis wall-associated protein. The Rhs core ORFs consist of two distinct parts: a large N-terminal core that is conserved in all Rhs elements, and a smaller C-terminus that is highly variable. Distinctive G+C contents of Rhs components indicate that the elements have a recent origin outside the E. coli species, and that they are composites assembled from segments with very different evolutionary histories. The Rhs cores fall into three sub-families that are mutually more than 20% divergent. Downstream of the core ORF is a second, much shorter ORF. Like the adjacent core extension, these are highly variable. In most examples, the hypothetical product of this ORF has a candidate signal sequence for transport across the cytoplasmic membrane. Another Rhs component, the 1.3 kb H-rpt, has features typical of insertion sequences. Structures homologous to H-rpt have been detected in other bacterial genera, such as Vibrio and Salmonella, where they are associated with loci that determine O-antigen variation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Base Sequence
  • DNA Transposable Elements
  • DNA, Bacterial / genetics*
  • Escherichia coli / genetics*
  • Molecular Sequence Data
  • Open Reading Frames*
  • Repetitive Sequences, Nucleic Acid / genetics*

Substances

  • Bacterial Proteins
  • DNA Transposable Elements
  • DNA, Bacterial