The 5' region of cnf1 harbours a translational regulatory mechanism for CNF1 synthesis and encodes the cell-binding domain of the toxin

Mol Microbiol. 1999 Jul;33(1):108-18. doi: 10.1046/j.1365-2958.1999.01453.x.

Abstract

The Escherichia coli cytotoxic necrotizing factor 1 (CNF1) is organized into three functional domains: the N-terminal part containing the cell-binding domain, a putative central membrane-spanning region, and a C-terminal catalytic region. On the basis of competition assays between CNF1 and GST-recombinant proteins containing different N-terminal fragments, and point mutations, we restricted the binding region to the first 190 amino acids. Hydrophilic amino acids 53-75 are strictly necessary to cell receptor recognition. Using different cnf1-lacZ translational fusions, we demonstrated that the mRNA corresponding to the first 48 codons of cnf1 is involved in the translational regulation of CNF1 synthesis. This regulation consists of both a positive and a negative control. The positive control is exerted by codons 6-20, including a putative downstream box that enhances the translational expression of cnf1. The negative control depends on codons 45-48. In this region, an anti-Shine-Dalgarno sequence, highly homologous to the core of the internal complementary sequence already reported for growth rate-regulated metabolic genes, has been detected. To some extent, the inner structural organization of CNF1 would thus suggest the compiling of several functions in a single mRNA protein system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions / genetics*
  • Bacterial Toxins / genetics*
  • Binding Sites
  • Cell Line / metabolism
  • Codon / genetics
  • Cytotoxins / genetics*
  • Escherichia coli / genetics*
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial / genetics*
  • Mutagenesis, Site-Directed
  • Protein Biosynthesis*
  • RNA, Bacterial / genetics
  • RNA, Messenger / genetics
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / genetics
  • Regulatory Sequences, Nucleic Acid*
  • Sequence Deletion
  • Sequence Homology, Nucleic Acid

Substances

  • 5' Untranslated Regions
  • Bacterial Toxins
  • Codon
  • Cytotoxins
  • Escherichia coli Proteins
  • RNA, Bacterial
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • cytotoxic necrotizing factor type 1