Disease relevance of lon

• In addition, the native transposase is stabilized in lon- strains of Escherichia coli, and, in these protease-deficient strains, trans action of transposase is increased 10- to 100-fold [1].
• Hybrid proteins encoded by recombinant phage accumulate in strains defective in protein degradation (lon mutants) in amounts amenable to large-scale purification [2].
• In contrast to the parent strain, the Brucella abortus lon mutant, designated GR106, was impaired in its capacity to form isolated colonies on solid medium at 41 degrees C and displayed an increased sensitivity to killing by puromycin and H2O2 [3].
• The lon protease from Mycobacterium smegmatis: molecular cloning, sequence analysis, functional expression, and enzymatic characterization [4].
• The lonD gene is homologous to the lon gene encoding an ATP-dependent protease and is essential for the development of Myxococcus xanthus [5].

High impact information on lon

• To determine whether the presence of abnormal proteins stimulates expression of this gene, we examined its transcription using a lon-lacZ operon fusion [6].
• It is the degradation-deficient property of lon mutants that is responsible for the suppression of the temperature-sensitive phenotype [7].
• One revertant, Tr29, was mapped to the lon region of the chromosome [7].
• They were mucoid, and sensitive to ultraviolet light and the radiomimetic agent nitrofurantoin, which are characteristics of lon mutants [7].
• We found that overexpressing Lon, which is mutated for the serine active site (LonS679A) and is therefore devoid of proteolytic activity, unexpectedly led to complementation of the UV sensitivity and capsule overproduction of a lon deletion mutant [8].

Chemical compound and disease context of lon

• We have previously found that plasmids carrying the Escherichia coli alp gene (now to be called alpA) suppress two phenotypes of a delta lon protease mutant, overproduction of capsular polysaccharide and sensitivity to UV light [9].
• The lon gene of Escherichia coli encodes the ATP-dependent serine protease La and belongs to the family of sigma 32-dependent heat shock genes [10].
• capR (lon) mutants of Escherichia coli K-12 are mucoid and sensitive to ultraviolet (UV) and X-ray radiation as well as to nitrofurantoin [11].
• The effects of postirradiation incubation with various chemicals structurally related to pantolactone on the survival of ultraviolet-irradiated Escherichia coli lon and ruv mutants were examined [12].

Biological context of lon

• Suppression of these lon phenotypes is most likely explained by the increased degradation of the Lon substrates responsible for these phenotypes [9].
• We have used Tn10 and lambda placMu mutagenesis to identify a chromosomal locus, slpA, that is required for alpA+ suppression of delta lon [9].
• Proteolysis by the lon (capR) protein required ATP hydrolysis [13].
• Induction of the heat shock response with ethanol had little or no effect in htpR mutants but stimulated lon transcription 2-3 fold in wild-type cells and htpR cells carrying pFN97 [14].
• In cells carrying additional copies of the lon gene under the control of the lac or tac promoter, induction of the protease resulted in a rapid cessation of cell growth and in a loss of viability at stationary phase [15].

Anatomical context of lon

• Cytoplasmic membrane fraction that promotes septation in an Escherichia coli lon mutant [16].
• An unstable 20-kDa fragment of the large subunit of human cytochrome b558, an integral membrane protein in phagocytes, is subject to proteolytic degradation even when produced in the lon-deficient BL21 strain [17].

Associations of lon with chemical compounds

• The cells with increased content of protease La (due to the lon plasmid or induction of the lon gene) exhibited severalfold higher rates of degradation of abnormal proteins containing amino acid analogs and of incomplete polypeptides containing puromycin [15].
• Mutations in lon cause a defect in the intracellular degradation of abnormal and mutant proteins and lead to a number of phenotypic changes, such as UV sensitivity and overproduction of capsular polysaccharide [18].
• Constitutively elevated levels of AppppA stimulate lon-independent proteolysis only in heat-shocked cells [19].
• The lon::delta Tn10 mutations and a lon deletion retaining only the amino-terminal 25% of the gene did not affect the energy-dependent degradation of proteins during starvation and led to only a 40 to 60% reduction in the ATP-dependent degradation of canavanine-containing proteins and puromycyl peptides [18].
• Also, the mucoid phenotype of K-12 lon strains grown on minimal glucose agar plates at 37 C was not significantly effected in sul derivatives [20].

Analytical, diagnostic and therapeutic context of lon

• We have partially purified another ATP-dependent protease from lon-cells that lack protease La (as shown by immunoblotting) [21].
• Furthermore, the amount of lon-specific mRNA is increased after salt, ethanol, and oxidative stress as well as after treatment with puromycin [10].
• Northern and Western blot analyses indicated that expression of lon is induced by elevated temperature, albeit to a much lower level than that of groEL [22].
• Our RT-PCR analysis revealed an elevation of expression of the oxyS gene in the lon mutant [23].

References