L-Arabinose system

Although the control for the L-arabinose system is positive (that is, in the absence of the specific regulatory gene, no expression of the operon occurs), it has recently been shown to have a negative element. Evidence indicates that the product of the regulatory gene araC is a protein which can exist in two different functionally active configurations that of a repressor and that of an activator, the transition from... 

Controlling sites are those genetic elements that are located at the beginning of an operon, which control the expression of the structural gene in that operon by cis dominant effects (Fig. 6) [20]. In the L-arabinose system the following controlling elements are indicated ... 

The effect of mutations in one structural gene on the activity of an adjacent structural gene in an operon was discovered in the L-arabinose system [2,73]. Certain mutations in gene araB were found to produce a coordinate decrease or increase in inducible levels of L-arabinose isomerase and L-ribulose 5-phosphate 4-epimerase as compared to corresponding levels found in the wild type [2,5,37]. In addition, mutations in the araA gene were found to produce increased inducible levels of L-ribulokinase [2], while some mutations effected a decrease in inducible levels of the epimerase [40]. Moreover, the increases or... 

Calculations of the electronic structures of a series of carbo-hydrates using the CNDO/2 method have produced linear relationships between C-n.m.r. chemical shifts and the atomic charges for the - and /3-D-glucose, u- and d-D-galactose and /3-L-arabinose systems. Model systems, treated by the RHF/ST0-3G method, have been used to evaluate the anomeric -and A effects in simple and 1-0-methylpyrano-sides and hence derive their conformational and anoraeric energies. 

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