Gene structure of the OmpA protein, a major surface protein of Escherichia coli required for cell-cell interaction

Abstract

The DNA sequence of the gene for the ompA protein, a major outer membrane protein of Escherichia coli, has been determined. The messenger RNA for the protein was deduced to consist of 140, 1038 and 46 bases for the 5′ end untranslated, the coding and the 3′ end untranslated regions, respectively. In the mRNA, 25 stable stem-and-loop structures (total ΔG = −215 kcal) can be formed, which cover the entire mRNA except for a sequence of 99 bases around the ribosome-binding site and the initiation codon. The secondary structure at the 3′ end of the mRNA shows a remarkable similarity in respect of the termination codon and the transcription termination signal with the mRNA for the lipoprotein, another major outer membrane protein. From the DNA sequence, the ompA protein was found to consist of 325 amino acid residues and is produced from a secretory precursor, pro-ompA protein, having a signal peptide of 21 extra amino acid residues at the amino terminal end. The codon usage is unusual and as much as 76% of the total amino acid residues are coded only by 17 codons. The DNA sequence of a fused gene between the ompA gene and an unknown gene from a cloning vector, pMF21, was also determined. In the hybrid protein produced by the fused gene 96 residues from the carboxyl terminus of the ompA protein were replaced with five residues from the gene from pMF21. However, the hybrid protein can still confer the sensitivity against ompA protein-specific phage, suggesting that the ompA protein can be incorporated without 30% of the protein from its carboxyl terminus into the outer membrane.