Disease relevance of xylA

• The genes xylA and xylB were cloned together with their promoter region from the chromosome of Klebsiella pneumoniae var. aerogenes 1033 and the DNA sequence (3225 bp) was determined [1].
• This also resulted in overproduction of plasmid-encoded xylose isomerase and xylulokinase activities in recombinant E. coli cells [1].
• A 3-kb region, located downstream of the Lactobacillus brevis xylA gene (encoding D-xylose isomerase), was cloned in Escherichia coli TG1 [2].
• The xylose isomerase-encoding gene (xylA) of Clostridium thermosaccharolyticum: cloning, sequencing and phylogeny of XylA enzymes [3].
• The xylA gene coding for xylose isomerase from the hyperthermophile Thermotoga neapolitana 5068 was cloned, sequenced, and expressed in Escherichia coli [4].

High impact information on xylA

• Selective cloning of Bacillus subtilis xylose isomerase and xylulokinase in Escherichia coli genes by IS5-mediated expression [5].
• Molecular cloning, DNA structure and expression of the Escherichia coli D-xylose isomerase [6].
• The deduced amino acid sequence of thermophilic C. thermosulfurogenes xylose isomerase displayed higher homology with those of thermolabile xylose isomerases from Bacillus subtilis (70%) and Escherichia coli (50%) than with those of thermostable xylose isomerases from Ampullariella (22%), Arthrobacter (23%), and Streptomyces violaceoniger (24%) [7].
• These results establish that the NH2-terminal methionine of xylose isomerase is specified by an ATG which is 7 nucleotides downstream from a Shine-Dalgarno sequence [8].
• Nucleotide sequence of the Bacillus subtilis xylose isomerase gene: extensive homology between the Bacillus and Escherichia coli enzyme [9].

Chemical compound and disease context of xylA

• E. coli wild-type cells which harbored plasmids with the intact xylAKp 5' upstream region in high copy number (but lacking an active xylB gene on the plasmids) were phenotypically xylose-negative and xylose isomerase and xylulokinase activities were drastically diminished [1].
• The gene that encodes thermostable glucose isomerase in Clostridium thermosulfurogenes was cloned by complementation of glucose isomerase activity in a xylA mutant of Escherichia coli [10].
• A central region of 2.9 kbp complemented an xylA (for xylene oxygenase) mutant of Pseudomonas putida mt-2 and was also capable of conferring the ability to convert indole to indigo on strains of Escherichia coli and P. putida [11].
• In the present study, the xylA gene encoding a thermostable xylose (glucose) isomerase was cloned from Streptomyces chibaensis J-59 [12].
• The structure of rhamnose isomerase from Escherichia coli and its relation with xylose isomerase illustrates a change between inter and intra-subunit complementation during evolution [13].

Biological context of xylA

• Moreover, in mineral medium containing a sugar mixture of 5% glucose and 2.5% xylose, oxygen-deprived strain CRX2 cells simultaneously consumed both sugars, demonstrating the absence of diauxic phenomena relative to the new xylA-xylB construct, albeit glucose-mediated regulation still exerted a measurable influence on xylose consumption kinetics [14].
• Deletion of 5' upstream regions of xylA on these plasmids and their substitution by a lac promoter resulted in a xylose-positive phenotype [1].
• The identification and mapping of xyl gene promoters suggest that the xylA and xylB genes are organized as an operon having a single xylose inducible promoter preceding the xylA gene [15].
• The gene (xylA) that encodes it has been cloned by complementing a xylA mutant of the ancestral strain, with the use of a shuttle vector [16].
• Deletion of 184 bp from the 5' part of the xylA reading frame reduces glucose repression to only twofold [17].

Associations of xylA with chemical compounds

• Glycerol, ribose, and arabinose exert only a basal twofold repression of the xyl operon, which is independent of the presence of the cis-active glucose-responsive element within the xylA reading frame [17].
• The existence of a functional XylR was further suggested by the presence of xylO sequences upstream of xylA and xylT and by the requirement of D-xylose for the induction of D-xylose isomerase, D-xylulose kinase, and D-xylose transport activities in L. brevis [2].
• Gene order of the TOL catabolic plasmid upper pathway operon and oxidation of both toluene and benzyl alcohol by the xylA product [18].
• A comparison with other known structures reveals that rhamnose isomerase is most similar to xylose isomerase [13].
• The available structural data suggest that a metal-mediated hydride-shift mechanism, which is generally favored for xylose isomerase, is also feasible for rhamnose isomerase [13].

Other interactions of xylA

• Controlled expression mediated by the suppressor was demonstrated for the lacZ and xylA amber mutants [19].
• In E. coli, complementation was achieved through integration of ispF at the araBAD locus with control from the arabinose-inducible araBAD promoter, while in B. subtilis, yacN was placed at amyE under control of the xylose-inducible xylA promoter [20].
• As an example of the general utility, we demonstrate treA expression under xylA-operator-promoter control [21].

Analytical, diagnostic and therapeutic context of xylA

• Subcloning and DNA restriction mapping allowed us to locate the xylA and xylB genes on a 1.6 kbp Bg/II fragment and a 2.6 kbp HindIII-Sa/I fragment, respectively [15].
• The xylM and xylA genes encode 35- and 40-kilodalton polypeptides, respectively, which were shown by genetic complementation tests to be subunits of xylene oxygenase [22].
• Molecular cloning and expression of a thermostable xylose (glucose) isomerase gene, xylA, from Streptomyces chibaensis J-59 [12].
• Sequence analysis showed that the site of IS5 insertion is 195 bp upstream from the putative ATG initiation codon of the xylose isomerase structural gene [5].
• The mechanism of xylose isomerase (EC 5.3.1.5) has been studied with X-ray crystallography [23].

References