The elongation factor 1 a (aEF-la) was purified to homogeneity from the thermoacidophilic archaebacterium Suljolobus soljataricus by chromatographic procedures utilising DEAE-Sepharose, hydroxyapatite and FPLC on Mono S. The purified protein binds [3H]GDP at a 1 : 1 molar ratio and it is essential for poly(Phe) synthesis in vitro; it also binds GTP but not ATP. These findings indicate that aEF-la is the counterpart of the eubacterial elongation factor Tu (EF-Tu).Purified aEF-la is a monomeric protein with a relative molecular mass of 49000 as determined by SDSjPAGE and by gel filtration on Sephadex G-300; its isoelectric point is 9.1. The overall amino acid composition did not reveal significant differences when compared with the amino acid composition of eubacterial EF-Tu from either Escherichia coli or Thermus thermophilus, of eukaryotic EF-la from Artemia salina or of archaebacterial EF-la from Methanococcus vannielii. The close similarities between the average hydrophobicity and the numbers of hydrogen-bond-forming or non-helix-forming residues suggest that common structural features exist among the factors compared.aEF-1 a shows remarkable thermophilic properties, as demonstrated by the rate of [3H]GDP binding which increases with temperature, reaching a maximum at 95°C; it is also quite heat-resistant, since after a 6-h exposure at 60°C and 87°C the residual [3H]GDP-binding ability was still 90% and 54% of the control, respectively.The affinity of aEF-la for GDP and GTP was also evaluated. At 80°C Kb for GDP was about 30-fold higher than Ki for GTP; at the same temperature Ki for GDP was 1.7 pM and Ki for GTP was 50 pM; these values were 300-fold and 100-fold higher, respectively, than those reported for E. coli EF-Tu at 30°C; compared to the values at 0°C of EF-Tu from E. coli and T. thermophilus or EF-la from A . salina, pig liver and calf brain, smaller differences were observed with eukaryotic factors. At 80°C kL GDP and k ; GDP of aEF-la were 7.8 min-' and 4.6 min-' . pM-', respectively; comparison with the values attributed to E. coli EF-Tu at 30°C indicates that the dissociation rate constant increases and the association rate constant decreases, thus indicating that the higher Ki for GDP of aEF-la is due to a synchronous alteration of the rates of both the dissociation and the association processes between GDP and aEF-1 a.Besides aEF-la, the other two elongation factors, aEF-2 and aEF-lP were also present in S. solfataricus, as suggested by the occurrence of reactions typical of each of them. This allows the hypothesis that in this extremophilic archaebacterium the protein synthesis process follows the same general pattern found in all other living organisms.Extremophilic archaebacteria live under unusual conditions of temperature, pH and salt concentration. Their proteins are receiving increasing attention since they are characterized by a great resistance to chemical and physical agents which are deleterious to the homologous proteins isolated from organisms living under normal conditions [l -31....

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Epidemiological studies have shown that a reduced risk of chronic diseases such as cancer and cardiovascular diseases is correlated with a regular consumption of fruits and vegetable, many of which are rich in polyphenols. The additive and synergistic effect of phytochemicals in fruits and vegetables may reduce chronic diseases related to oxidative stress in human body. Olea europaea L. leaf are rich in phenolic components, which have been proposed to play a role in cancer prevention. The purpose of this study was to identify the main components in the Olea europaea L. leaf (cv. Leccino) preserved during the decoction preparation, in order to delineate the antioxidant activities of the crude extracts and its isolated compounds by using different in vitro assays including DPPH radicalscavenging capacity, total antioxidant capacity (TAC), xanthine oxidase (XO) inhibitory effect and the ability to delay the linoleic acid peroxidation process (ALP). The aqueous decoction was partitioned obtaining four extracts and the n-butanol extract showed the highest antioxidant activity and the highest total phenolic content. Phytochemical investigation leads to the isolation of thirteen secondary metabolites including simple phenolics, flavonoids, secoiridoids whose structures were elucidated by spectroscopic data (1D and 2D NMR) and spectrometric techniques. A significant free radical scavenging effect against DPPH has been evidenced in fraxamoside (1) (EC50 62.6 µM) and taxifolin (5) (EC50 50.0 µM), isolated for the first time from the water decoction. The most active compound in the TAC evaluation, was the 3,4 dihydro-phenyl glycol (8) (0.90 caffeic acid equiv.) while taxifolin and fraxamoside resulted as the most efficient inhibitors of XO activity (IC50 2.7 and 5.2 µM, respectively). Secoxyloganin (4), oleuropein (2) and tyrosol (6) showed the highest ALP activity. This study adds to the growing body of data supporting the bioactivities of phytochemicals and their potential impact on human health.

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