title: Disruption of rpmJ encoding ribosomal protein L36 decreases the expression of secY upstream of the spc operon and inhibits protein translocation in Escherichia coli.
abstract: The spc operon of Escherichia coli encodes 11 ribosomal proteins and SecY. The secY gene and downstream rpmJ encoding a ribosomal protein, L36, are located distal to the promoter of the spc operon. It has been suggested that the stability of SecY mRNA depends on rpmJ unless a rho-independent terminator is inserted immediately downstream of secY. Moreover, it has been suggested that RpmJ is dispensable for E. coli. We constructed rpmJ null strains, AY101 (DeltarpmJ::tetA) and AY201 (DeltarpmJ::cat), by replacing rpmJ with tetA, which encodes a membrane protein responsible for tetracycline-resistance, and cat, which encodes a cytoplasmic chloramphenicol acetyltransferase, respectively. Depletion of RpmJ did not inhibit protein synthesis, whereas the growth of AY101 was defective at high temperatures. The level of SecY mRNA decreased significantly in both disruptants even though the rho-independent terminator was inserted immediately downstream of secY. Some periplasmic proteins were missing in the disruptants with a concomitant increase in the amount of phage shock protein in the inner membrane. These phenotypes caused by the rpmJ null mutation were corrected by a plasmid carrying secY, but not by one carrying rpmJ.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
authors.forename: Ayao
authors.initials: A
authors.lastname: Ikegami
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Nishiyama
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Matsuyama
authors.forename: Hajime
authors.initials: H
authors.lastname: Tokuda
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D021381:Protein Transport; D012269:Ribosomal Proteins / Q000235:genetics*; D000069816:SEC Translocation Channels
chemical_list: D017931:DNA Primers; D029968:Escherichia coli Proteins; D012269:Ribosomal Proteins; D000069816:SEC Translocation Channels; C057841:SecY protein, E coli