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The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
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X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
5.
ERIC S. BONO PATRICK SMOLINSKI AL CASAGRANDA JUNDE XU 《Computer methods in biomechanics and biomedical engineering》2013,16(2):125-131
The Shear-slip Mesh Update Method (SSMUM) is being used in flow simulations involving large but regular displacements of one or more boundaries of the computational domain. We follow up the earlier discussion of the method with notes on practical implementation aspects. In order to establish a benchmark problem for this class of flow problems, we define and report results from a two-dimensional viscous flow around a rotating stirrer in a square chamber. The application potential of the method is demonstrated in the context of biomedical design problem, as we perform an analysis of blood flow in a centrifugal left ventricular assist device, or blood pump, which involves a rotating impeller in a non-axisymmetric housing. 相似文献
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HENRY SILVERMAN BABIKER AHMED SAMAR AJEILET SUMAIA AL‐FADIL SUHAIL AL‐AMAD HADIR EL‐DESSOUKY IBRAHIM EL‐GENDY MOHAMED EL‐GUINDI MUSTAFA EL‐NIMEIRI RANA MUZAFFAR AZZA SALEH 《Developing world bioethics》2010,10(2):70-77
To help ensure the ethical conduct of research, many have recommended educational efforts in research ethics to investigators and members of research ethics committees (RECs). One type of education activity involves multi‐day workshops in research ethics. To be effective, such workshops should contain the appropriate content and teaching techniques geared towards the learning styles of the targeted audiences. To ensure consistency in content and quality, we describe the development of a curriculum guide, core competencies and associated learning objectives and activities to help educators organize research ethics workshops in their respective institutions. The curriculum guide is divided into modular units to enable planners to develop workshops of different lengths and choose content materials that match the needs, abilities, and prior experiences of the target audiences. The content material in the curriculum guide is relevant for audiences in the Middle East, because individuals from the Middle East who participated in a Certificate Program in research ethics selected and developed the training materials (e.g., articles, powerpoint slides, case studies, protocols). Also, many of the activities incorporate active‐learning methods, consisting of group work activities analyzing case studies and reviewing protocols. The development of such a workshop training curriculum guide represents a sustainable educational resource to enhance research ethics capacity in the Middle East. 相似文献
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van der Sluis C Smit BA Hartmans S ter Schure EG Tramper J Wijffels RH 《Enzyme and microbial technology》2000,27(1-2):151-156
To elucidate the growth inhibitory effect of threonine, the regulation of the aspartate-derived amino-acid metabolism in Zygosaccharomyces rouxii, an important yeast for the flavor development in soy sauce, was investigated. It was shown that threonine inhibited the growth of Z. rouxii by blocking the methionine synthesis. It seemed that threonine blocked this synthesis by inhibiting the conversion of aspartate. In addition, it was shown that the growth of Z. rouxii, unlike that of Saccharomyces cerevisiae, was not inhibited by the herbicide sulfometuron methyl (SMM). From enzyme assays, it was concluded that the acetohydroxy acid synthase in Z. rouxii, unlike that in S. cerevisiae, was not sensitive to SMM. Furthermore, the enzyme assays demonstrated that the activity of threonine deaminase in Z. rouxii, like in S. cerevisiae, was strongly inhibited by isoleucine and stimulated by valine. From this work, it is clear that the aspartate-derived amino-acid metabolism in Z. rouxii only partly resembles that in S. cerevisiae. 相似文献
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Immobilized soy-sauce yeasts: development and characterization of a new polyethylene-oxide support 总被引:4,自引:0,他引:4
van der Sluis C Mulder AN Grolle KC Engbers GH ter Schure EG Tramper J Wijffels RH 《Journal of biotechnology》2000,80(2):179-188
Entrapment of cells in alginate gel is a widely used mild immobilization procedure. However, alginate gel is not very suitable for use in long-term continuous soy-sauce processes because alginate is sensitive to abrasion and chemically unstable towards the high salt content of soy-sauce medium. Therefore, a chemically crosslinked polyethylene-oxide gel was used instead. The disadvantage of this gel was that due to the crosslinking reaction, the viability of the cells after immobilization was poor. For this reason, a new mild procedure for immobilizing soy-sauce yeasts in polyethylene-oxide gel was developed, resulting in high survival percentages of the soy-sauce yeasts Zygosaccharomyces rouxii and Candida versatilis. This newly developed polyethylene-oxide gel, unlike alginate gel, appeared not to be sensitive to abrasion, even in the presence of high salt concentrations. Therefore, we concluded that this newly developed polyethylene-oxide gel is more suitable than alginate gel for use as immobilization material in long-term processes with a high salt content, like soy-sauce processes. 相似文献
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