ABSTRACT
In Escherichia coli, iron assimilation by means of the siderophore enterobactin requires two hydrophobic cytoplasmic membrane proteins, FepD and FepG, which are essential components of a binding-protein-dependent transport system. Such components are typically difficult to detect. Here we report observation of the fepD and fepG gene products in polyacrylamide gels; they appeared as diffuse bands at positions consistent with smaller sizes than those predicted by sequence analysis. Translational coupling was suggested by the lack of a detectable product from the fepG message in the absence of translation of the upstream fepD message. The orientation of FepD/FepG in the membrane was predicted based on their similarities in sequence and hydrophobicity to FhuB.
Subject(s)
Bacterial Outer Membrane Proteins/isolation & purification , Carrier Proteins/isolation & purification , Escherichia coli/enzymology , Receptors, Cell Surface , Bacterial Outer Membrane Proteins/genetics , Base Sequence , Carrier Proteins/genetics , Escherichia coli/genetics , Gene Expression Regulation, Bacterial , Iron/metabolism , Molecular Sequence Data , Nucleic Acid Conformation , Protein Biosynthesis , Protein Structure, Secondary , Protein Structure, TertiaryABSTRACT
Transposon mutagenesis and plasmid complementation studies have identified two genes, fepD and fepG, which are essential for ferrienterobactin transport in Escherichia coli. These genes mapped in the enterobactin gene cluster and genetic evidence indicated that they are transcribed as part of an operon (fepD, fepG, fepC). The nucleotide sequence of fepD was determine; it could encode a hydrophobic 33.8 kDa protein with sequence homologies to other iron and vitamin B12 transport proteins. Also identified, between fepD and fepB, was an open reading frame (ORF43) with no detectable function; its 43 kDa protein product (P43) was seen on polyacrylamide gels. The fepD-C operon and ORF43 were divergently transcribed from a 110bp region containing a binding site for the repressor protein Fur.
Subject(s)
Bacterial Outer Membrane Proteins/genetics , Carrier Proteins/genetics , Escherichia coli/genetics , Membrane Transport Proteins/genetics , Receptors, Cell Surface , Amino Acid Sequence , Base Sequence , Binding Sites/genetics , Genetic Complementation Test , Iron/metabolism , Molecular Sequence Data , Multigene Family/genetics , Mutagenesis, Insertional , Open Reading Frames/genetics , Operon/genetics , Plasmids/genetics , Restriction MappingABSTRACT
The Escherichia coli gene for the ferrienterochelin uptake and colicins B and D receptor protein is located at approximately 13 min, adjacent to or among genes for enterochelin biosynthetic enzymes. The two receptor functions (colicin and siderophore) are separable by mutation.
Subject(s)
Bacterial Proteins/biosynthesis , Colicins/pharmacology , Enterobactin/metabolism , Escherichia coli/genetics , Genes , Receptors, Drug/biosynthesis , Serine/analogs & derivatives , Chromosome Mapping , Chromosomes, Bacterial , Colicins/metabolism , Escherichia coli/metabolismABSTRACT
Gordon, Irving (University of Southern California, Los Angeles), Sara S. Chenault, Douglas Stevenson, and Jean D. Acton. Effect of interferon on polymerization of single-stranded and double-stranded mengovirus ribonucleic acid. J. Bacteriol. 91:1230-1238. 1966.-The effect of interferon on actinomycin-resistant mengovirus ribonucleic acid (RNA) replication in L cells was investigated to determine whether defective or partially polymerized RNA products were made and whether synthesis of any specific class of virus RNA was prevented. RNA labeled with uridine-C(14) was extracted in hot and cold phenol and analyzed by zonal sucrose density centrifugation. Both single- and double-stranded infectious RNA peaks were identified. Interferon treatment caused almost complete depression of uridine-C(14) incorporation throughout linear sucrose gradients except in the 4S region, and no infectivity was detectable in any fraction. These inhibitory effects are attributable to the action of interferon, because they were reversed when cultures were treated with actinomycin D simultaneously with interferon. The results, with those of other investigators, indicate that the step at which interferon interrupts virus multiplication is between the events immediately after uncoating and the formation of template "minus" strands; under the conditions of our experiments, no partially polymerized virus RNA products were made.
