title: Transient erythromycin resistance phenotype associated with peptidyl-tRNA drop-off on early UGG and GGG codons.
abstract: Expression of minigenes encoding tetra- or pentapeptides MXLX or MXLXV (E peptides), where X is a nonpolar amino acid, renders cells erythromycin resistant whereas expression of minigenes encoding tripeptide MXL does not. By using a 3A' reporter gene system beginning with an E-peptide-encoding sequence, we asked whether the codons UGG and GGG, which are known to promote peptidyl-tRNA drop-off at early positions in mRNA, would result in a phenotype of erythromycin resistance if located after this sequence. We find that UGG or GGG, at either position +4 or +5, without a following stop codon, is associated with an erythromycin resistance phenotype upon gene induction. Our results suggest that, while a stop codon at +4 gives a tripeptide product (MIL) and erythromycin sensitivity, UGG or GGG codons at the same position give a tetrapeptide product (MILW or MILG) and phenotype of erythromycin resistance. Thus, the drop-off event on GGG or UGG codons occurs after incorporation of the corresponding amino acid into the growing peptide chain. Drop-off gives rise to a peptidyl-tRNA where the peptide moiety functionally mimics a minigene peptide product of the type previously associated with erythromycin resistance. Several genes in Escherichia coli fulfill the requirements of high mRNA expression and an E-peptide sequence followed by UGG or GGG at position +4 or +5 and should potentially be able to give an erythromycin resistance phenotype.
authors.affiliation: Department of Genetics, Microbiology and Toxicology, Stockholm University, Svante Arrhenius väg 16F, 106 91 Stockholm, Sweden.
authors.forename: Mirjana
authors.initials: M
authors.lastname: Macvanin
authors.forename: Ernesto I
authors.initials: EI
authors.lastname: Gonzalez de Valdivia
authors.forename: David H
authors.initials: DH
authors.lastname: Ardell
authors.forename: Leif A
authors.initials: LA
authors.lastname: Isaksson
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003062:Codon / Q000235:genetics*; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects*; D017930:Genes, Reporter; D009842:Oligopeptides / Q000096:biosynthesis; D014176:Protein Biosynthesis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D013205:Staphylococcal Protein A / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D003062:Codon; D009842:Oligopeptides; D012346:RNA, Transfer, Amino Acyl; D013205:Staphylococcal Protein A; C019037:tRNA, peptidyl-; D004917:Erythromycin