In Escherichia coli, the AraC protein represses transcription from its own promoter, PC, and when associated with arabinose, activates transcription from three other promoters, PBAD, PE, and PFGH. Expression from all four of these promoters is also regulated by cyclic AMP-catabolite activator protein; however, the arrangement of the protein binding sites is not identical for each promoter. We a...

Efficient and cost-effective fuel ethanol production from lignocellulosic materials requires simultaneous cofermentation of all hydrolyzed sugars, mainly including D-glucose, D-xylose, and L-arabinose. Saccharomyces cerevisiae is a traditional D-glucose fermenting strain and could utilize D-xylose and L-arabinose after introducing the initial metabolic pathways. The efficiency and simultaneous ...

l-Arabinose was metabolized through an oxidative pathway by extracts of a strain of Rhizobium japonicum. The findings showed that l-arabinose is converted into 2-keto-3-deoxy-l-arabonate, which is cleaved into glycoaldehyde and pyruvate.

We applied two experiments useful in the study of ligand-regulated DNA binding proteins to AraC, the dimeric regulator of the Escherichia coli l-arabinose operon. In the absence of arabinose, AraC prefers to loop DNA by binding to two half-sites that are separated by 210 base pairs, and in the presence of arabinose it prefers to bind to adjacently located half-sites. The basis for this ligand-r...

Agricultural and agro-industrial residues (agro-residues) containing high amounts of carbohydrates, such as cellulose and hemicellulose, are produced in large amounts annually worldwide.1,2 Agro-residues are attractive raw materials of biorefinery processes producing value-added products due to their relatively low commercial value, renewability and abundant availability.3 Biorefining of agro-r...

The previously isolated hemiplegic, induction-negative, repression-positive mutants, H80R and Y82C, were found to be defective in the binding of arabinose. Randomization of other residues close to arabinose in the three-dimensional structure of AraC or that make strong interactions with arabinose yielded induction-negative, repression-positive mutants. The induction and repression properties of...

I,-Arabinosr is transported into Escherichia coli via two independent transport systems, a system possessing relatively low affinity for arabinose, the araE system, and a system of higher affinity for arabinose, t)he araFG system. In the work reported here we demonstrate that insert,ion of the Mu-Zac bacteriophage isolated by Casadaban 8r Cohen (1979) permits a reliable measurement’ of the expr...

The dimeric AraC protein of Escherichia coli binds specifically to DNA sequences upstream of promoters whose transcription is regulated by arabinose. Here we show with affinity measurements, DNase footprinting, dimethyl sulfate premethylation interference and dimethyl sulfate footprinting studies that AraC protein can recognize paired half-sites in direct repeat orientation or inverted repeat o...

The biocatalytic reduction of D-xylose to xylitol requires separation of the substrate from L-arabinose, another major component of hemicellulosic hydrolysate. This step is necessitated by the innate promiscuity of xylose reductases, which can efficiently reduce L-arabinose to L-arabinitol, an unwanted byproduct. Unfortunately,due to the epimeric nature of D-xylose and L-arabinose, separation c...