Binding States of Protein–Metal Complexes in Cells

The identification of endogenous proteins as well as their binding to metal ions in living cells is determined by combining pulsed electrophoretic separations with nanoelectrospray ionization followed by mass spectrometric detection. This approach avoids problems resulting from the complicated cellular environment. In this manner, we demonstrate the rapid identification (300 ms or less) of intact proteins from living E. coli cells including the complexation of calmodulin with calcium ion. The latter showed different binding states from those observed in in vitro studies. These observations also reveal in vitro measurements do not necessarily represent the actual situation in living cells. We conclude that the attempted in situ measurement of intracellular proteins with minimal sampling processes should be preferred

Reliable Tracking In-Solution Protein Unfolding via Ultrafast Thermal Unfolding/Ion Mobility-Mass Spectrometry

Sequential unfolding of monomeric proteins is important for the global understanding of local conformational elements (e.g., secondary structures and domain connections) within those protein assemblies. Ion mobility-mass spectrometry (IM-MS) is an emerging and promising technique for probing gradual protein structural perturbations in the gas phase. However, it is still challenging to track sequential unfolding in the solution phase. Here, we extended IM-MS to track in-solution sequential unfolding of monomeric proteins having single and/or multidomains. The present method combines ultrafast local heating effect (LHE)-driven sequential unfolding with IM-MS identification. Protein sequential unfolding in solution is demonstrated by the rapid and controllable IM-MS data switch between native and gradually unfolded states. Our results show that LHE induces gradual protein conformational transitions associated with biological functions, where IM-MS tracks the sequential unfolding of monomeric proteins

Discovery of potential novel microsomal triglyceride transfer protein inhibitors via virtual screening of pharmacophore modelling and molecular docking

<p>In order to identify potential natural inhibitors against the microsomal triglyceride transfer protein (MTP), HipHop models were generated using 20 known inhibitors from the Binding Database. Using evaluation indicators, the best hypothesis model, Hypo1, was selected and utilised to screen the Traditional Chinese Medicine Database, which resulted in a hit list of 58 drug-like compounds. A homology model of MTP was built by MODELLER and was minimised by CHARMm force field. It was then validated by Ramachandran plot and Verify-3D so as to obtain a stable structure, which was further used to refine the 58 hits using molecular docking studies. Then, five compounds with higher docking scores which satisfied the docking requirements were discovered. Among them, Ginkgetin and Dauricine were most likely to be candidates that exhibition inhibiting effect on MTP. The screening strategy in this study is relatively new to the discovery of MTP inhibitors in medicinal chemistry. Moreover, it is important to note that, lomitapide, an approved MTP inhibitor, fits well with Hypo1 as well as our homology model of MTP, which confirmed the rationality of our studies. The results indicated the applicability of molecular modeling for the discovery of potential natural MTP inhibitors from traditional Chinese herbs.</p

Using “On/Off” ¹⁹F NMR/Magnetic Resonance Imaging Signals to Sense Tyrosine Kinase/Phosphatase Activity in Vitro and in Cell Lysates

Tyrosine kinase and phosphatase are two important, antagonistic enzymes in organisms. Development of noninvasive approach for sensing their activity with high spatial and temporal resolution remains challenging. Herein, we rationally designed a hydrogelator Nap-Phe-Phe­(CF₃)-Glu-Tyr-Ile-OH (<b>1a</b>) whose supramolecular hydrogel (i.e., Gel <b>1a</b>) can be subjected to tyrosine kinase-directed disassembly, and its phosphate precursor Nap-Phe-Phe­(CF₃)-Glu-Tyr­(H₂PO₃)-Ile-OH (<b>1b</b>), which can be subjected to alkaline phosphatase (ALP)-instructed self-assembly to form supramolecular hydrogel Gel <b>1b</b>, respectively. Mechanic properties and internal fibrous networks of the hydrogels were characterized with rheology and cryo transmission electron microscopy (cryo-TEM). Disassembly/self-assembly of their corresponding supramolecular hydrogels conferring respective “On/Off” ¹⁹F NMR/MRI signals were employed to sense the activity of these two important enzymes <i>in vitro</i> and in cell lysates for the first time. We anticipate that our new ¹⁹F NMR/magnetic resonance imaging (MRI) method would facilitate pharmaceutical researchers to screen new inhibitors for these two enzymes without steric hindrance