title: Yersinia yopQ mRNA encodes a bipartite type III secretion signal in the first 15 codons.
abstract: The type III machinery of Yersinia transports Yop proteins across the bacterial envelope. The minimal secretion signal of yopQ is located in codons 1-10 that, when fused in frame to the neomycin phosphotransferase gene, is sufficient to promote type III secretion of YopQ(1-10)-Npt. Frame-shift mutations, generated by nucleotide insertions or deletions following the AUG start and suppressed at the fusion site with npt, abrogate signalling of yopQ(1-10) but not of yopQ(1-15). By generating transversions of every single nucleotide in yopQ(1-10), we identified 10 nucleotide positions in codons 2, 3, 5, 7, 9 and 10 that were each required for substrate recognition. One transversion that abolishes secretion, uridyl 9 to adenyl (U9A), is a synonymous codon 3 mutation that retains the original amino acid as confirmed by Edman degradation analysis, suggesting that the mRNA but not the amino acid sequence of yopQ(1-10) is involved in secretion signalling. Although transversion of U8A abrogates signalling of yopQ(1-10), fusion of yopQ codons 11-15 restores secretion. The nucleotides that are required for this suppression by yopQ(11-15) were identified and revealed both synonymous and non-synonymous mutations. Frame-shift mutations introduced into just this suppressor region (codons 11-15) did not abrogate its ability to suppress mutations in the minimal secretion signal (codons 1-10). Thus, elements downstream of the minimal secretion signal of YopQ increase the efficiency of YopQ secretion and suppress mutations elsewhere in the secretion signal.
authors: Committee on Microbiology, University of Chicago, Chicago, Illinois 60637, USA.
authors: Kumaran S
authors: KS
authors: Ramamurthi
authors: Olaf
authors: O
authors: Schneewind
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D003062:Codon; D016368:Frameshift Mutation; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D015008:Yersinia enterocolitica / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003062:Codon; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C067570:YopQ protein, Yersinia enterocolitica