title: Genetic interaction between the Escherichia coli AcpT phosphopantetheinyl transferase and the YejM inner membrane protein.
abstract: Strain LH530, a mutant of Escherichia coli K-12, was reported by others to show increased outer membrane permeability, temperature-sensitive growth, and reduced synthesis of lipid A. The unmapped mutant gene was found to be suppressed by high-copy-number plasmids carrying the wild-type acpT gene, which encodes a protein that catalyzes a post-translational protein modification, the attachment of 4'-phosphopantetheine. We mapped the strain LH530 mutation to a gene of unknown function, yejM, known to encode an inner membrane protein. The mutation is a yejM nonsense mutation that produces a truncated protein lacking the predicted periplasmic domain. Reconstruction of the mutation gave a strain having the same phenotypes as LH530. In contrast to the nonsense mutants, deletion of the entire yejM gene was lethal. Suppression by AcpT overexpression of the yejM nonsense mutants encoding the truncated proteins was specific to AcpT. Moreover, AcpT overexpression also suppressed the lethality due to deletion of the entire yejM gene and this suppression also did not require that AcpT be enzymatically active. The mechanism whereby overexpression of a specific cytosolic protein bypasses the essentiality of an inner membrane protein is unknown.
authors.affiliation: Department of Biochemistry, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: De Lay
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D002876:Chromosomes, Bacterial / Q000235:genetics; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics*; D017353:Gene Deletion; D020043:Genes, Essential; D005816:Genetic Complementation Test; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism; D018869:Heat-Shock Response; D010641:Phenotype; D013489:Suppression, Genetic; D013696:Temperature; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; C529531:YejM protein, E coli; C082662:phosphopantetheinyl transferase; D017855:Transferases (Other Substituted Phosphate Groups)