Browsing by Author "McKenzie, J. M."
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- ItemRapid analysis of major components and potential authentication of South African olive oils by quantitative ¹³C nuclear magnetic resonance spectroscopy(Academy of Science for South Africa, 2004) McKenzie, J. M.; Koch, K. R.We have developed a rapid, quantitative ¹³C NMR spectroscopic method for the determination of the major fatty acids (oleic, linoleic and saturated acids) contained as triacylglycerides in South African extra-virgin olive oils. With the judicious use of a shiftless NMR relaxation agent, Cr(acetylacetonate)3, it is possible to determine the principal fatty acids in 0.4 g of olive oil within 20 min. This method also allows for the estimation of the distribution of the oleic and linoleic acids in the naturally occurring triacylglycerides in olive oils, expressed as α/β ratios for the triacylglycerides. Moreover, a fake product, marketed in South Africa as an 'extra-virgin olive oil', was also analysed to demonstrate the use of ¹³C NMR spectroscopy as a rapid means of establishing the authenticity of the claimed product on the local market. We further examined a selection of extra-virgin olive oils produced in various regions of the Western Cape province in 2002 and 2003, using ¹³C NMR spectroscopy, in a preliminary attempt to determine their major fatty acid compositions, and to establish whether any regional and cultivar-based differences in these products can thereby be detected.
- ItemSolution structure of RING finger-like domain of retinoblastoma-binding protein-6 (RBBP6) suggests it functions as a U-box(2012) Kappo, M. A.; Ab, E.; Hassem, F.; Atkinson, R. A.; Faro, A.; Muleya, V.; Mulaudzi, T.; Poole, J. O.; McKenzie, J. M.; Chibi, M.; Moolman-Smook, J. C.; Rees, D. J. G.; Pugh, D. J. R.Retinoblastoma-binding protein-6 (RBBP6) plays a facilitating role, through its RING finger-like domain, in the ubiquitination of p53 by Hdm2 that is suggestive of E4-like activity. Although the presence of eight conserved cysteine residues makes it highly probable that theRINGfinger-like domain coordinates two zinc ions, analysis of the primary sequence suggests an alternative classification as a member of the U-box family, the members of which do not bind zinc ions. We show here that despite binding two zinc ions, the domain adopts a homodimeric structure highly similar to those of a number of U-boxes. Zinc ions could be replaced by cadmium ions without significantly disrupting the structure or the stability of the domain, although the rate of substitution was an order of magnitude slower than any previous measurement, suggesting that the structure is particularly stable, a conclusion supported by the high thermal stability of the domain. A hallmark of U-box-containing proteins is their association with chaperones, with which they cooperate in eliminating irretrievably unfolded proteins by tagging them for degradation by the proteasome. Using a yeast two-hybrid screen, we show that RBBP6 interacts with chaperones Hsp70 and Hsp40 through its N-terminal ubiquitin-like domain. Taken together with the structural similarities to U-box-containing proteins, our data suggest that RBBP6 plays a role in chaperone-mediated ubiquitination and possibly in protein quality control. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A.