Farhad Abdulkarim

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The genes coding for the translation factor EF-Tu, tufA and tufB are separated by over 700 kb on the circular chromosome of Salmonella typhimurium. The coding regions of these genes have 99% identity at the nucleotide level in spite of the presumed ancient origin of the gene duplication. Sequence comparisons between S. typhimurium and Escherichia coli(More)
Three protein factors IF1, IF2 and IF3 are involved in the initiation of translation in prokaryotes. No clear function has been assigned to the smallest of these three factors, IF1. Therefore, to investigate the role of this protein in the initiation process in Escherichia coli we have mutated the corresponding gene infA. Because IF1 is essential for cell(More)
The antibiotic kirromycin inhibits protein synthesis by binding to EF-Tu and preventing its release from the ribosome after GTP hydrolysis. We have isolated and sequenced a collection of kirromycin resistant tuf mutations and identified thirteen single amino acid substitutions at seven different sites in EF-Tu. These have been mapped onto the 3D structures(More)
We have used a simple selection and screening method to isolate function defective mutants of EF-Tu. From 28 mutants tested, 12 different missense substitutions, individually lethal to some essential function of EF-Tu, were identified by sequencing. In addition we found a new non-lethal missense mutation. The frequency of isolation of unique mutations(More)
Uneven distribution of plasmid-based expression vectors to daughter cells during bacterial cell division results in an increasing proportion of plasmid free cells during growth. This is a major industrial problem leading to reduction of product yields and increased production costs during large-scale cultivation of vector-carrying bacteria. For this reason,(More)
Mutations affecting a region of the Escherichia coli RNA polymerase have been isolated that specifically reduce the copy number of ColE1-type plasmids. The mutations, which result in a single amino acid alteration (G1161R) or a 41-amino acid deletion (Δ1149–1190) are located near the 3′-terminal region in the rpoC gene, which encodes the largest subunit(More)
An Escherichia coli strain was constructed in which both chromosomal genes encoding elongation factor (EF)-Tu (tufA and tufB) have been inactivated with precise coding sequence replacements. A tufA gene in an expression vector is supplied as the sole EF-Tu source. By using plasmid replacement, based on plasmid incompatibility, mutant EF-Tu variants with a(More)
Five single amino acid substitution variants of EF-Tu from Salmonella typhimurium were tested for their ability to promote poly(U)-translation in vitro. The substitutions are Leu120 Gln, Gln124 Arg and Tyr160 (Asp or Asn or Cys). They were selected by their kirromycin resistant phenotypes and all substitutions are in domain I at the interface between(More)
Direct measurements of the rates of dissociation of dipeptidyl-tRNA from the ribosome show that hyperaccurate SmP and SmD ribosomes have unstable A-site binding of peptidyl-tRNA, while P-site binding is extremely stable in relation to the wild type. Error-prone Ram ribosomes, on the other hand, have stable A-site and unstable P-site binding of(More)
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