l -ARABINOSE-SENSITIVE, l -RIBULOSE 5-PHOSPHATE 4-EPIMERASE-DEFICIENT MUTANTS OF ESCHERICHIA COLI

Abstract

Arabinose-negative mutants of Escherichia coli B/r, ara-53 and ara-139, are deficient in the enzyme L-ribulose 5-phosphate 4-epimerase; ara-53, further analyzed, accumulates large quantities of L-ribulose 5-phosphate when incubated with L-arabinose. The mutant sites are closely linked to the left of the previously ordered L-arabinose mutant sites, and probably represent the structural gene for L-ribulose 5-phosphate 4epimerase (gene D) in the L-arabinose operon. The inducible levels of L-arabinose isomerase and L-ribulose 5-phosphate 4-epimerase vary correspondingly as a result of mutation in the structural gene for L-ribulokinase (gene B), further substantiating the dual structural and regulatory function of this gene locus. Ara-53 and ara-139 are strongly inhibited by L-arabinose and give rise to L-arabinose-resistant mutants. The one resistant mutant analyzed still lacks the 4-epimerase but is deficient in L-ribulokinase and has increased L-arabinose isomerase activity, a characteristic of a type of mutation in the B gene. It is proposed that accumulation of Lribulose 5-phosphate is responsible for the inhibition, and that mutation to resistance will involve mutation in the A, B, C, permease, or repressor genes, thus providing a direct method for isolating these types of L-arabinose-negative mutants. Glucose prevents and cures the Larabinose inhibition.

TatD is a central component of a Tat translocon‐initiated quality control system for exported FeS proteins in Escherichia coli

“…Arabinose-resistant derivatives of MC4100 and DtatABCDE were used as described previously (Guzman et al, 1995;Bolhuis et al, 2000). The strain DtatD was made arabinose resistant as described previously (Englesberg et al, 1962). E. coli was grown aerobically at 37 1C in Luria-Bertoni broth (Bolhuis et al, 2000).…”

Simultaneous uptake of lignocellulose‐based monosaccharides by Escherichia coli

“…5A), growth was barely detected and did not commence logarithmically until after approximately 20 h had passed (not shown in graph). This is likely explained by the lack of glucose-mediated CCR, which allows an immediate uptake of L-arabinose, and since this leads to toxic metabolite accumulation in the cell (Englesberg et al, 1962), growth Figure 4. Stability of L-arabinose utilization by strain AF1000ara.…”

Malfolded recombinant Tat substrates are Tat‐independently degraded in Escherichia coli

“…However, when L-arabinose-dependent expression systems are to be used, care must be taken to select for L-arabinose-resistant clones, as MC4100 is an araD-mutant strain and L-arabinose inhibits growth. The accumulation of ribulose-P in the metabolism of L-arabinose has been proposed to be the reason for the growth inhibition by L-arabinose [19]. Selection on L-arabinose-containing media readily results in suppressor strains that have mutations in araB, araA, araC or L-arabinose uptake systems and therefore cannot accumulate ribulose-P [19].…”

“…The accumulation of ribulose-P in the metabolism of L-arabinose has been proposed to be the reason for the growth inhibition by L-arabinose [19]. Selection on L-arabinose-containing media readily results in suppressor strains that have mutations in araB, araA, araC or L-arabinose uptake systems and therefore cannot accumulate ribulose-P [19]. Any of these mutations are expected to have different effects on cytoplasmic arabinose levels and thus individually selected L-arabinose-resistant clones are likely to differ in the expression levels when arabinose-inducible promoters are used.…”