Practical and reliable FRET/FLIM pair of fluorescent proteins

Background  

In spite of a great number of monomeric fluorescent proteins developed in the recent years, the reported fluorescent protein-based FRET pairs are still characterized by a number of disadvantageous features, complicating their use as reporters in cell biology and for high-throughput cell-based screenings.     

A nonheme iron(II) complex that models the redox cycle of lipoxygenase

The air-stable complex [Fe(6-Me3-TPA) (O2CAr)]+ [1; 6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine] has been synthesized as a model for the iron(II) site of lipoxygenase. This iron(II) complex reacts with 0.5 equiv ROOH to form a yellow species, which has been formulated as [FeIII(OH)(6-Me3-TPA) (O2CAr)]+ (2) by electrospray mass spectrometry. Addition of more ROOH converts 2 into a purple species, which is characterized by electrospray ionization mass spectrometry and resonance Raman spectroscopy as [FeIII(OOR)(6-Me3-TPA)(O2CAr)]+. The purple species is metastable and decomposes via Fe-O bond homolysis to regenerate the starting iron(II) complex. These metal-centered transformations parallel the changes observed for lipoxygenase in its reaction with its product hydroperoxide.     

The Novel Responses of Ethambutol Against <Emphasis Type="Italic">Mycobacterium smegmatis</Emphasis> mc<Superscript>2</Superscript>155 Revealed by Proteomics Analysis

Ethambutol (EMB), one of the effective anti-mycobacterial drugs, inhibits the biosynthesis of mycobacterium cell wall. To elucidate the molecular mechanism of EMB against tuberculosis (TB), Mycobacterium smegmatis mc²155 was employed as a model of mycobacterial system in this study. We compared the protein profiles on M. smegmatis mc²155 treated by EMB and untreated using fluorescence difference two-dimensional gel electrophoresis (2-D DIGE). A total of 40 differential protein spots were selected and 22 proteins were identified by HPLC-nano ESI–MS/MS analysis, including 16 over-expressed proteins and 6 under-expressed proteins. These proteins mainly affected energy metabolism, as well as synthesis and modification of macromolecules. The expressions of correspondent genes were confirmed by RT-PCR. This investigation provided some clues for searching potential drug targets.     

Mechanisms of proton inhibition and sensitization of the cation channel TRPV3

TRPV3 is a temperature-sensitive, nonselective cation channel expressed prominently in skin keratinocytes. TRPV3 plays important roles in hair morphogenesis and maintenance of epidermal barrier function. Gain-of-function mutations of TRPV3 have been found in both humans and rodents and are associated with hair loss, pruritus, and dermatitis. Here, we study the mechanisms of acid regulation of TRPV3 by using site-directed mutagenesis, fluorescent intracellular calcium measurement, and whole-cell patch-clamp recording techniques. We show that, whereas extracellular acid inhibits agonist-induced TRPV3 activation through an aspartate residue (D641) in the selectivity filter, intracellular protons sensitize the channel through cytoplasmic C-terminal glutamate and aspartate residues (E682, E689, and D727). Neutralization of the three C-terminal residues presensitizes the channel to agonist stimulation. Molecular dynamic simulations revealed that charge neutralization of the three C-terminal residues stabilized the sensitized channel conformation and enhanced the probability of α-helix formation in the linker between the S6 transmembrane segment and TRP domain. We conclude that acid inhibits TRPV3 function from the extracellular side but facilitates it from the intracellular side. These novel mechanisms of TRPV3 proton sensing can offer new insights into the role of TRPV3 in the regulation of epidermal barrier permeability and skin disorders under conditions of tissue acidosis.     

A novel plant actin-microtubule bridging complex regulates cytoskeletal and ER structure at ER-PM contact sites

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