The functional L-asparaginase from Escherichia coli is a homotetramer with a molecular weight of about 142 kDa. The X-ray structure of the enzyme, crystallized in a new form (space group C2) and refined to 1.95 A resolution, is compared with that of the previously determined crystal form (space group P2(1)). The asymmetric unit of the new crystal form contains an L-asparaginase dimer instead of the tetramer found in the previous crystal form. It is found that crystal contacts practically do not affect the conformation of the protein. It is shown that subunit C of the tetrameric form is in a conformation which is systematically different from that of all other subunits in both crystal forms. Major conformational differences are confined to the lid loop (residues 14-27). In addition, the stability of this globular protein is analyzed in terms of the interactions between hydrophobic parts of the subunits.

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These results provide evidence that the fructose 2,6-bisphosphate level in T. reesei is independent of cAMP concentrations and not related to a CAMP-dependent mechanism, but to the availability of substrate fructose 6-phosphate.

In grape production, cover crops play a key role in soil protection and nutrient cycling. Thus, since grapevine requirements for P are low, adequate management of cover crops may provide sufficient P for growth. This paper evaluates the effect of black oats, as a cover plant, on the P solubilization in rock phosphate and its availability to the vine cultivated in succession. To test this hypothesis, we evaluated the plants growth parameters and P uptake in grapevines grown in succession to black oats in pots in a greenhouse experiment. The results showed that the soil sterilization decreased P availability to black oats, but not to grapevine. The soil fertilization with rock phosphate increased the P accumulation in oat and grapevine plants, although no further effect was observed from the use the cover crop. The plant height and dry mass contents were higher for grapevine in soils fertilized with rock phosphate and covered with black oats.