Dsb‐Verbindung: Der Redoxpfad, der Reduktionsäquivalente aus dem bakteriellen Cytoplasma über die innere Membran zu den drei reduktiven Dsb‐Pfaden im ansonsten oxidierenden Periplasma überführt ...(siehe Schema; TR=Thioredoxin‐Reduktase, Trx=Thioredoxin) wurde aus den aufgereinigten Komponenten rekonstituiert. Der Transfer der Reduktionsäquivalente über die Membran wurde nachgewiesen, und Details des Mechanismus wurden aufgeklärt.
► Definition of nanomaterials is prerequisite for regulation of nanomaterials. ► Current status of various regulatory frameworks of the EU with regard to nanomaterials. ► Issues relevant for ...regulation and areas for scientific contributions indicated. ► Major issues: nano-related risks for non-nanomaterials, measurement techniques, changes during life cycle.
In recent years, an increasing number of applications and products containing or using nanomaterials have become available. This has raised concerns that some of these materials may introduce new risks for humans or the environment. A clear definition to discriminate nanomaterials from other materials is prerequisite to include provisions for nanomaterials in legislation. In October 2011 the European Commission published the ‘Recommendation on the definition of a nanomaterial’, primarily intended to provide unambiguous criteria to identify materials for which special regulatory provisions might apply, but also to promote consistency on the interpretation of the term ‘nanomaterial’. In this paper, the current status of various regulatory frameworks of the European Union with regard to nanomaterials is described, and major issues relevant for regulation of nanomaterials are discussed. This will contribute to better understanding the implications of the choices policy makers have to make in further regulation of nanomaterials. Potential issues that need to be addressed and areas of research in which science can contribute are indicated. These issues include awareness on situations in which nano-related risks may occur for materials that fall outside the definition, guidance and further development of measurement techniques, and dealing with changes during the life cycle.
The lactose transport protein (LacS) of Streptococcus thermophilus belongs to a family of transporters in which putative α-helices II and IV have been implicated in cation binding and the coupled ...transport of the substrate and the cation. Here, the analysis of site-directed mutants shows that a positive and negative charge at positions 64 and 71 in helix II are essential for transport, but not for lactose binding. The conservation of charge/side-chain properties is less critical for Glu-67 and Ile-70 in helix II, and Asp-133 and Lys-139 in helix IV, but these residues are important for the coupled transport of lactose together with a proton. The analysis of second-site suppressor mutants indicates an ion pair exists between helices II and IV, and thus a close approximation of these helices can be made. The second-site suppressor analysis also suggests ion pairing between helix II and the intracellular loops 6–7 and 10–11. Because the C-terminal region of the transmembrane domain, especially helix XI and loop 10–11, is important for substrate binding in this family of proteins, we propose that sugar and proton binding and translocation are performed by the joint action of these regions in the protein. Indeed, substrate protection of maleimide labeling of single cysteine mutants confirms that α-helices II and IV are directly interacting or at least conformationally involved in sugar binding and/or translocation. On the basis of new and published data, we reason that the helices II, IV, VII, X, and XI and the intracellular loops 6–7 and 10–11 are in close proximity and form the binding sites and/or the translocation pathway in the transporters of the galactosides-pentosides-hexuronides family.
Biochemistry. A missing link in membrane protein evolution Poolman, Bert; Geertsma, Eric R; Slotboom, Dirk-Jan
Science (American Association for the Advancement of Science),
2007-Mar-02, 20070302, Letnik:
315, Številka:
5816
Journal Article
The lactose transport protein (LacS) of Streptococcus thermophilus belongs to a family of transporters in which putative α-helices II and IV have been implicated in cation binding and the
coupled ...transport of the substrate and the cation. Here, the analysis of site-directed mutants shows that a positive and negative
charge at positions 64 and 71 in helix II are essential for transport, but not for lactose binding. The conservation of charge/side-chain
properties is less critical for Glu-67 and Ile-70 in helix II, and Asp-133 and Lys-139 in helix IV, but these residues are
important for the coupled transport of lactose together with a proton. The analysis of second-site suppressor mutants indicates
an ion pair exists between helices II and IV, and thus a close approximation of these helices can be made. The second-site
suppressor analysis also suggests ion pairing between helix II and the intracellular loops 6â7 and 10â11. Because the C-terminal
region of the transmembrane domain, especially helix XI and loop 10â11, is important for substrate binding in this family
of proteins, we propose that sugar and proton binding and translocation are performed by the joint action of these regions
in the protein. Indeed, substrate protection of maleimide labeling of single cysteine mutants confirms that α-helices II and
IV are directly interacting or at least conformationally involved in sugar binding and/or translocation. On the basis of new
and published data, we reason that the helices II, IV, VII, X, and XI and the intracellular loops 6â7 and 10â11 are in close
proximity and form the binding sites and/or the translocation pathway in the transporters of the galactosides-pentosides-hexuronides
family.
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