AraC protein, a transcriptional regulator of the L-arabinose operon in Escherichia coli, is dimeric. Each monomer consists of a domain for DNA binding plus transcription activation and a domain for dimerization plus arabinose binding. These are connected to one another by a linker region of at least 5 amino acids. Here we have addressed the question of whether any of the amino acids in the link...

Uridine diphosphate (UDP)-arabinose 4-epimerase (EC 5.1.3.5) has been purified at least 20-fold from wheat germ by MnCl(2) treatment, (NH(4))(2)SO(4) fractionation, dialysis, and Sephadex and diethylaminoethyl cellulose column chromatography. The enzyme has no action on UDP-d-glucose, UDP-d-glucuronic acid, or TDP-d-glucose. The pH optimum is 8.0. Km values are 1.5 mM for UDP-d-xylose and 0.5 m...

A new plating medium using bromothymol blue (BTB) indicator is described and compared with eosin-methylene blue (EMB), MacConkey, and Endo media. These media were tested with L-arabinose by plating fermenting and nonfermenting mutant strains of Escherichia coli. The minimum concentrations of L-arabinose that permitted differentiation of these strains were determined. Different concentrations we...

TIG December 2000, volume 16, No. 12 559 Over forty years of research on the L-arabinose operon of Escherichia coli have provided insights into the mechanism of positive regulation of gene activity. This research also discovered DNA looping and the mechanism by which the regulatory protein changes its DNA-binding properties in response to the presence of arabinose. As is frequently seen in focu...

Rhizobia have a versatile catabolism that allows them to compete successfully with other microorganisms for nutrients in the soil and in the rhizosphere of their respective host plants. In this study, Bradyrhizobium japonicum USDA 110 was found to be able to utilize oxalate as the sole carbon source. A proteome analysis of cells grown in minimal medium containing arabinose suggested that oxalat...

After addition of l-arabinose to growing Escherichia coli, the l-ribulokinase (EC 2.7.1.16) and l-arabinose isomerase (EC 5.3.1.4) first appear at about 0.7 and 1.4 min, respectively. These times are consistent with the distances of the genes from the ribonucleic acid polymerase initiation site in the operon. The kinetics of appearance of these enzymes as well as those of beta-galactosidase (EC...

Fractionation of pectic polysaccharides from the juice of ripening ;Bartlett' pears (Pyrus communis) gave two general types of polyuronides. The major type was a homogalacturonan (HGA) whose molecular weight decreased upon ripening. The other type comprised heteropolymers composed of various amounts of arabinose, rhamnose, and galactose. Treatment of the major arabinose-containing heteropolymer...

1. An experimental system suitable for the study of enzyme formation has been described. 2. The formation of beta-galastosidase in E. coli B could be induced by lactose, melibiose, D-galactose and beta-methyl-D-galactoside. 3. Lactose-induced beta-galactosidase formation was found to be inhibited by D-glucose, D-mannose, D-fructose, D-arabinose, and raffinose. 4. The utilizable structural analo...