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11.
FLO gene-dependent phenotypes in industrial wine yeast strains 总被引:1,自引:0,他引:1
Patrick Govender Michael Bester Florian F. Bauer 《Applied microbiology and biotechnology》2010,86(3):931-945
Most commercial yeast strains are nonflocculent. However, controlled flocculation phenotypes could provide significant benefits
to many fermentation-based industries. In nonflocculent laboratory strains, it has been demonstrated that it is possible to
adjust flocculation and adhesion phenotypes to desired specifications by altering expression of the otherwise silent but dominant
flocculation (FLO) genes. However, FLO genes are characterized by high allele heterogeneity and are subjected to epigenetic regulation. Extrapolation of data obtained
in laboratory strains to industrial strains may therefore not always be applicable. Here, we assess the adhesion phenotypes
that are associated with the expression of a chromosomal copy of the FLO1, FLO5, or FLO11 open reading frame in two nonflocculent commercial wine yeast strains, BM45 and VIN13. The chromosomal promoters of these
genes were replaced with stationary phase-inducible promoters of the HSP30 and ADH2 genes. Under standard laboratory and wine making conditions, the strategy resulted in expected and stable expression patterns
of these genes in both strains. However, the specific impact of the expression of individual FLO genes showed significant differences between the two wine strains and with corresponding phenotypes in laboratory strains.
The data suggest that optimization of the flocculation pattern of individual commercial strains will have to be based on a
strain-by-strain approach. 相似文献
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Lauren K. Pietersen Patrick Govender Hendrik G. Kruger Glenn E. M. Maguire James Wesley-Smith Thavendran Govender 《International journal of peptide research and therapeutics》2010,16(4):291-295
By designing and coupling two functional peptides, CKAFKRK and C(KAFKRK)3 in differing ratios to the surface of gold nanoparticles (GNPs), we evaluated the effect of loading on aggregation and proteolysis. Transmission electron microscopy images of the functionalised GNPs indicated a direct relationship between the degree of aggregation of the particles and the extent of peptide loading: The greater the percentage of the C(KAFKRK)3 peptide, the greater the dispersion (less aggregation) of the peptide-capped GNPs. The functionalised GNPs were subjected to trypsin digestion over increasing time periods and it was found that the peptides were cleaved at the site of Lys and Arg. The extent of cleavage was analysed by mass spectrometry. The results indicate that the rate of enzymatic degradation was directly proportional to the extent of loading, such that the greater percentage of the C(KAFKRK)3 peptide, the greater the rate and efficiency of the cleavage. These results could be attributed to the different peptide distribution of the particles and the entropy of the peptides with varying peptide ratios. 相似文献
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Bahareh Honarparvar Sachin A Pawar Cláudio Nahum Alves Jer?nimo Lameira Glenn EM Maguire José Rogério A Silva Thavendran Govender Hendrik G Kruger 《Journal of biomedical science》2015,22(1)
Background
Novel pentacycloundecane (PCU)-lactone-CO-EAIS peptide inhibitors were designed, synthesized, and evaluated against wild-type C-South African (C-SA) HIV-1 protease. Three compounds are reported herein, two of which displayed IC50 values of less than 1.00 μM. A comparative MM-PB(GB)SA binding free energy of solvation values of PCU-lactam and lactone models and their enantiomers as well as the PCU-lactam-NH-EAIS and lactone-CO-EAIS peptide inhibitors and their corresponding diastereomers complexed with South African HIV protease (C-SA) was performed. This will enable us to rationalize the considerable difference between inhibitory concentration (IC50) of PCU-lactam-NH-EAIS and PCU-lactone-CO-EAIS peptides.Results
The PCU-lactam model exhibited more negative calculated binding free energies of solvation than the PCU-lactone model. The same trend was observed for the PCU-peptide inhibitors, which correspond to the experimental activities for the PCU-lactam-NH-EAIS peptide (IC50 = 0.076 μM) and the PCU-lactone-CO-EAIS peptide inhibitors (IC50 = 0.850 μM). Furthermore, a density functional theory (DFT) study on the natural atomic charges of the nitrogen and oxygen atoms of the three PCU-lactam, PCU-lactim and PCU-lactone models were performed using natural bond orbital (NBO) analysis. Electrostatic potential maps were also used to visualize the electron density around electron-rich regions. The asymmetry parameter (η) and quadrupole coupling constant (χ) values of the nitrogen and oxygen nuclei of the model compounds were calculated at the same level of theory. Electronic molecular properties including polarizability and electric dipole moments were also calculated and compared. The Gibbs theoretical free solvation energies of solvation (∆Gsolv) were also considered.Conclusions
A general trend is observed that the lactam species appears to have a larger negative charge distribution around the heteroatoms, larger quadrupole constant, dipole moment and better solvation energy, in comparison to the PCU-lactone model. It can be argued that these characteristics will ensure better eletronic interaction between the lactam and the receptor, corresponding to the observed HIV protease activities in terms of experimental IC50 data.Electronic supplementary material
The online version of this article (doi:10.1186/s12929-015-0115-5) contains supplementary material, which is available to authorized users. 相似文献15.
Nelesh P. Govender Tom M. Chiller Bhavani Poonsamy John A. Frean 《Current fungal infection reports》2011,5(4):224-232
Despite the considerable morbidity and mortality associated with fungal diseases in sub-Saharan Africa, it is notable that
these diseases have been omitted from an expanded list of neglected tropical diseases. Inextricably tied together with HIV/AIDS
and tuberculosis in sub-Saharan Africa, important fungal diseases such as cryptococcal meningitis and Pneumocystis jirovecii pneumonia (PCP) manifest as relatively common and deadly AIDS-defining opportunistic infections, often masked by and comorbid
with tuberculosis. Others, such as mycetoma, which manifest as a debilitating and deforming illness primarily affecting rural
adults, directly affect the socioeconomic productivity of rural communities. Lack of adequate diagnostic tests makes identifying
the true disease burden due to fungal diseases difficult. To highlight the devastating impact of fungal diseases on the health
and socioeconomic circumstances of sub-Saharan Africa’s poorest people and to increase the profile of efforts to control and
prevent these diseases, we propose that the following fungal diseases be added to the list of neglected tropical diseases:
cryptococcal meningitis, PCP, mycetoma, histoplasmosis, sporotrichosis, and blastomycosis. By outlining the prevalence, distribution,
and disease burden of these fungal diseases in sub-Saharan Africa in this review, we hope to provide information to prioritize
strategies for detection, control, and prevention of the neglected fungal diseases. 相似文献
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Summary Immunocytochemical identification of skin cells are difficult due to numerous endogenous autofluorescent components within the cell and the environment. This is particularly evident in hair follicles. This paper reports on a serendipitous modification to an existing method which results in a drastically reduced background fluorescence. Immediately after antigen retrieval, sections exposed to 0.3% hydrogen peroxide in methanol for 30 min at room temperature exhibited low background fluorescence, increased antigenicity and revealed quantifiable numbers of melanocytes. This method is applicable to both human and mouse melanocytes particularly in the hair follicle. 相似文献
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Savanna ecosystems have long been fertile ground for mathematical modeling of vegetation structure and the role of resources and disturbance in tree-grass coexistence. In recent years, several authors have presented models that explore how savanna fires suppress the woody community, alter ecosystem dynamics, and promote grass persistence. We argue, however, that the assumption that fires influence savanna dynamics by consuming woody biomass may be wrong because, in reality, fires kill seedlings and saplings that constitute little biomass relative to adult trees. We present a simple alternative that separates the woody community into a subadult (fire-sensitive) class and an adult (fire-resistant) class and explore how this ecologically more realistic, but still simplified, model may provide better simulations of demographic processes and response to fires in savannas. 相似文献
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Vashni Gramany Algasan Govender Krishna Bisetty Suren Singh Kugenthiren Permaul 《Journal of biomolecular structure & dynamics》2016,34(8):1681-1692
The aim of this study was to clone, express, and characterize a β-xylosidase (Tlxyn1) from the thermophilic fungus Thermomyces lanuginosus SSBP in Pichia pastoris GS115 as well as analyze optimal activity and stability using computational and experimental methods. The enzyme was constitutively expressed using the GAP promoter and secreted into the medium due to the alpha-mating factor secretion signal present on the expression vector pBGPI. The 1276 bp gene consists of an open reading frame that does not contain introns. A 12% SDS–PAGE gel revealed a major protein band at an estimated molecular mass of 50 kDa which corresponded to zymogram analysis. The three-dimensional structure of β-xylosidase was predicted, and molecular dynamics simulations at different ranges of temperature and pH were performed in order to predict optimal activity and folding energy. The results suggested a strong conformational temperature and pH dependence. The recombinant enzyme exhibited optimal activity at pH 7 and 50°C and retained 80% activity at 50°C, pH 7 for about 45 min. This is the first report of the cloning, functional expression, and simulations study of a β-xylosidase from Thermomyces species in a fungal host. 相似文献