title: An Escherichia coli membrane protein with a unique signal sequence.
abstract: The smp gene, whose promoter divergently overlaps with the Escherichia coli serB promoter, encodes a 24-kDa membrane protein of unknown function. An smp fusion to the lacZ gene was constructed to select for smp promoter up-mutations. The mutations isolated, however, were located within the smp structural gene rather than within the promoter region. A 15-bp deletion and two different point mutations, corresponding to the hydrophobic region of the Smp signal sequence, resulted in a Lac+ phenotype. The point mutations introduced a positively charged amino acid into the hydrophobic region. The Smp signal sequence is unique in that it is encoded by an mRNA which has the potential to form a 9-bp hairpin structure with a 39-nt loop, that conforms to the idealized mirror symmetric sequence GC(RGUGR)(YUGUY)5 (RGUGR)CG. This highly symmetrical region may encode additional intragenic information important for the expression of smp. A computer search revealed that the smp gene product shares homology with elongation factor Ts and ribosomal subunit L4, two components of the E. coli translational apparatus.
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City 52242.
authors.forename: A F
authors.initials: AF
authors.lastname: Neuwald
authors.forename: G V
authors.initials: GV
authors.lastname: Stauffer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010445:Peptide Elongation Factors / Q000235:genetics; D021382:Protein Sorting Signals / Q000235:genetics*; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D010445:Peptide Elongation Factors; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; C023512:elongation factor Ts; C056368:ribosomal protein L4; C061825:ytjB protein, E coli