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921.
Seo PS Jeong JJ Zeng L Takoudis CG Quinn BJ Khan AA Hanada T Chishti AH 《Biochimica et biophysica acta》2009,1793(2):281-289
Direct physical linkage of MAGUKs to the actin cytoskeleton was first established by the interaction of erythrocyte p55 with the FERM domain of protein 4.1R. Subsequently, it was reported that p55 binds to a 51-amino acid peptide, encoded by exon 10, located within the FERM domain of protein 4.1R. In this study, we investigated the nature of the p55-FERM domain binding interface and show that p55 binds to a second 35-amino acid peptide, encoded by an alternatively spliced exon 5, located within the FERM domain of protein 4.1R. Competition and Surface Plasmon Resonance-binding measurements suggest that the peptides encoded by exons 5 and 10 bind to independent sites within the D5 domain of p55. Interestingly, the full length 135 kDa isoform of protein 4.1R containing both exons 5 and 10 was targeted exclusively to the plasma membrane of epithelial cells whereas the same isoform without exon 5 completely lost its membrane localization capacity. Together, these results indicate that p55 binds to two distinct sites within the FERM domain, and the alternatively spliced exon 5 is necessary for the membrane targeting of protein 4.1R in epithelial cells. Since sequences similar to the exon 5-peptide of protein 4.1R and D5 domain of p55 are conserved in many proteins, our findings suggest that a similar mechanism may govern the membrane targeting of other FERM domain containing proteins. 相似文献
922.
Christos Chinopoulos 《Biophysical journal》2009,96(6):2490-2504
A novel method exploiting the differential affinity of ADP and ATP to Mg2+ was developed to measure mitochondrial ADP-ATP exchange rate. The rate of ATP appearing in the medium after addition of ADP to energized mitochondria, is calculated from the measured rate of change in free extramitochondrial [Mg2+] reported by the membrane-impermeable 5K+ salt of the Mg2+-sensitive fluorescent indicator, Magnesium Green, using standard binding equations. The assay is designed such that the adenine nucleotide translocase (ANT) is the sole mediator of changes in [Mg2+] in the extramitochondrial volume, as a result of ADP-ATP exchange. We also provide data on the dependence of ATP efflux rate within the 6.8-7.8 matrix pH range as a function of membrane potential. Finally, by comparing the ATP-ADP steady-state exchange rate to the amount of the ANT in rat brain synaptic, brain nonsynaptic, heart and liver mitochondria, we provide molecular turnover numbers for the known ANT isotypes. 相似文献
923.
Christos Arvanitidis Paul John Somerfield Sofia Reizopoulou Anastasios Eleftheriou 《Journal of experimental marine biology and ecology》2009,369(2):100-109
It is accepted that observed patterns in community structure change as analyses are carried out at higher taxonomic levels. Univariate analyses which incorporate higher taxonomic structure within assemblages have been shown to be informative. In this paper we suggest ways in which changes in multivariate relationships at higher taxonomic levels and associated with higher taxonomic/phylogenetic structure of the community may be incorporated into multivariate analyses, an aspect never occurred before in this type of analysis. Four approaches, namely: biodiversity MDS (bdMDS), number of taxa MDS (ntMDS), delta MDS (δMDS) and lambda MDS (λMDS), are proposed, and applied to theoretical data as well as to data collected from the literature on the Mediterranean lagoonal environment. Results show that these approaches have the capacity to distinguish severely impacted lagoons from naturally disturbed ones, although in practice the simplest method (ntMDS) was the most successful. Analyses based on the most abundant groups (polychaetes, molluscs, crustaceans) did not always match analyses based on the entire macrofauna, mirroring the performance of taxonomic distinctness indices in the Mediterranean lagoons. The important characteristics of the approaches introduced, as well as potential criticisms are provided. Application of these techniques on smaller scales and to other habitats, is suggested prior to their wider use in the region. 相似文献
924.
Aikaterini A. Tzialla Ali A. Taha Emmanuel Kalogeris Haralambos Stamatis 《Biotechnology letters》2009,31(9):1451-1456
Ternary systems consisting of monoterpenes (α-pinene or d-limonene), tert-butanol and water were used as reaction media to enhance the catalytic performance of laccases from various fungi sources
(Trametes versicolor, T. hirsuta and Botrytis cinerea). The enzymes had improved catalytic efficiency (5- to 10-fold) in α-pinene-rich environment, while optimal reaction rates were in high-water content systems (15.5% v/v). The stability of laccases
was significantly improved in monoterpene-based systems (up to 90% residual enzyme activity after 24 h at 30°C) in comparison
with other non-conventional media. The results indicate that these ternary systems can increase the potential of laccases
as catalysts for various oxidations. 相似文献
925.
Vasileios A. Tatsis Ioannis G. Tsoulos Christos S. Krinas Charalampos Alexopoulos Athanassios Stavrakoudis 《International journal of biological macromolecules》2009,44(5):393-399
Resistance to cationic antimicrobial peptide polymyxin B from Gram-negative bacteria is accomplished by two-component systems (TCSs), protein complexes PmrA/PmrB and PhoP/PhoQ. PmrD is the first protein identified to mediate the connectivity between two TCSs. The 3D structure of PmrD has been recently solved by NMR and its unique fold was revealed. Here, a molecular dynamics study is presented started from the NMR structure. Numerous hydrophobic and electrostatic interactions were identified to contribute to PmrD's 3D stability. Moreover, the mobility of the five loops that connect the protein's six β-strands has been explored. Solvent-accessible surface area calculation revealed that a Leucine-rich hydrophobic cluster of the protein stabilized the protein's structure. 相似文献
926.
927.
Christina Krämer Holger Seltmann Markus Seifert Wolfgang Tilgen Christos C. Zouboulis Jörg Reichrath 《The Journal of steroid biochemistry and molecular biology》2009,113(1-2):9-16
Sebocytes are sebum-producing cells that form the sebaceous glands. We investigated the role of sebocytes as target cells for vitamin D metabolites and the existence of an enzymatic machinery for the local synthesis and metabolism of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3, calcitriol], the biologically active vitamin D metabolite, in these cell types. Expression of vitamin D receptor (VDR), vitamin D-25-hydroxylase (25OHase), 25-hydroxyvitamin D-1α-hydroxylase (1αOHase), and 1,25-dihydroxyvitamin D-24-hydroxylase (24OHase) was detected in SZ95 sebocytes in vitro using real time quantitative polymerase chain reaction. Splice variants of 1αOHase were identified by nested touchdown polymerase chain reaction. We demonstrated that incubation of SZ95 sebocytes with 1,25(OH)2D3 resulted in a cell culture condition-, time-, and dose-dependent modulation of cell proliferation, cell cycle regulation, lipid content and interleukin-6/interleukin-8 secretion in vitro. RNA expression of VDR and 24OHase was upregulated along with vitamin D analogue treatment. Although several other splice variants of 1αOHase were detected, our findings indicate that the full length product represents the major 1αOHase gene product in SZ95 cells. In conclusion, SZ95 sebocytes express VDR and the enzymatic machinery to synthesize and metabolize biologically active vitamin D analogues. Sebocytes represent target cells for biologically active metabolites. Our findings indicate that the vitamin D endocrine system is of high importance for sebocyte function and physiology. We conclude that sebaceous glands represent potential targets for therapy with vitamin D analogues or for pharmacological modulation of 1,25(OH)2D3 synthesis/metabolism. 相似文献
928.
Eirini Kretza Christos P. Papaneophytou Rigini M. Papi Konstantina Karidi Costas Kiparissides Dimitrios A. Kyriakidis 《Biotechnology and Bioprocess Engineering》2012,17(3):512-525
In this study, the lipolytic activity of Thermus thermophilus HB8 was examined. The addition of various oils increased the production of extracellular lipolytic activity, while a combination of olive oil and glucose increased both extracellular and intracellular lipolytic activity. The oxygen transfer rate had a significant influence on both biomass and production of extra- or intra-cellular lipolytic activity. The formation of white halos due to the hydrolysis of oleic acid ester (Tween 80) in agar plates containing Nile Blue and the formation of Ca2+-oleate indicated the secretion of lipase. When the cell-free supernatant of cells grown in basal reach medium or the corresponding intracellular extract were electrophoresed under denatured and renatured conditions, using ??-naphthyl acetate and Fast Blue RR, major bands at 56 kDa or 62 and 32 kDa were observed, respectively. The 56 kDa extracellular enzyme was partial purified and characterized. Its peak of activity occurred at 80°C and pH 7.0, while the T1/2 was 1 h at 100°C. The K m of the partial purified enzyme was 1 mM and the V max was 0.044 U/mL/min when using p-nitrophenyl laurate as substrate. The presence of Ca2+ and Hg2+ stimulated lipase activity, whereas Zn2+, Co2+, or EDTA inhibited lipase activity. The highest activity was observed in the presence of coconut oil and p-nitrophenyl laurate (pNPL). Purified lipase was the most stable in the presence of various organic solvents, such as pentanol, chloroform and n-dodecane. Because of the superior thermostability and stability in the presence of organic solvents of T. thermophilus extracellular lipase, this lipase holds great promise for use in industrial applications. 相似文献
929.
Charalampos Doukas Theodoros Petsatodis Christos Boukis Ilias Maglogiannis 《Biomedical signal processing and control》2012,7(3):256-264
Results of clinical studies suggest that there is a relationship between breathing-related sleep disorders and behavioral disorder and health effects. Apnea is considered one of the major sleep disorders with great accession in population and significant impact on patient's health. Symptoms include disruption of oxygenation, snoring, choking sensations, apneic episodes, poor concentration, memory loss, and daytime somnolence. Diagnosis of apnea and breath disorders involves monitoring patient's biosignals and breath during sleep in specialized clinics requiring expensive equipment and technical personnel. This paper discusses the design and technical details of an integrated low-cost system capable for preliminary detection of sleep breath disorders at patient's home utilizing patient sound signals. The paper describes the proposed architecture and the corresponding HW and SW modules, along with a preliminary evaluation. 相似文献
930.