Enzyme I of theEscherichia coliphosphoenolpyruvate:sugar phosphotransferase system undergoes a slow monomer-dimer transition.In vitroautophosphorylation of Enzyme I by PEP was studied at limiting ...concentrations of the protein. Addition to incubation mixtures containing wild-type Enzyme I of inactive or low-activity mutant forms of Enzyme I resulted in stimulation of autophosphorylation activity. The kinetics of the activation fit well to a model in which the active form of Enzyme I is the dimer. These experiments provide support for the argument that only the dimeric form of Enzyme I can be autophosphorylated.
The unphosphorylated form of enzyme IIAglc of the Escherichia coli phosphoenolpyruvate:sugar phosphotransferase system inhibits transport catalyzed by lactose permease. We (Seok et al. (1997) Proc. ...Natl. Acad. Sci. U.S.A. 94, 13515−13519) previously characterized the area on the cytoplasmic face of lactose permease that interacts with enzyme IIAglc, using radioactive enzyme IIAglc. Subsequent studies (Sondej et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 3525−3530) suggested consensus binding sequences on proteins that interact with enzyme IIAglc. The present study characterizes a region on the surface of enzyme IIAglc that interfaces with lactose permease. Acetylation of lysine residues by sulfosuccinimidyl acetate treatment of enzyme IIAglc, but not lactose permease, reduced the degree of interaction between the two proteins. To localize the lysine residue(s) on enzyme IIAglc that is(are) involved in the regulatory interaction, selected lysine residues were mutagenized. Conversion of nine separate lysines to glutamic acid resulted in proteins that were still capable of phosphoryl acceptance from HPr. Except for Lys69, all the modified proteins were as effective as the wild-type enzyme IIAglc in a test for binding to lactose permease. The Lys69 mutant was also defective in phosphoryl transfer to glucose permease. To derive further information concerning the contact surface, additional selected residues in the vicinity of Lys69 were mutagenized and tested for binding to lactose permease. On the basis of these studies, a model for the region of the surface of enzyme IIAglc that interacts with lactose permease is proposed.
Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der ...Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe3–x GeTe2 nanoflakes show a significant suppression of the magnetic anisotropy with hole doping. Electronic structure measurements and calculations reveal that the chemical potential shift associated with hole doping is responsible for the reduced magnetic anisotropy by decreasing the energy gain from the spin–orbit induced band splitting. Our findings provide an understanding of the intricate connection between electronic structures and magnetic properties in two-dimensional magnets and propose a method to engineer magnetic properties through doping.
Bacteria sense continuous changes in their environment and adapt metabolically to effectively compete with other organisms for limiting nutrients. One system which plays an important part in this ...adaptation response is the phosphoenol-pyruvate:sugar phosphotransferase system (PTS). Many proteins interact with and are regulated by PTS components in bacteria. Here we review the interaction with and allosteric regulation of Escherichia coli glycogen phosphorylase (GP) activity by the histidine phosphocarrier protein HPr, which acts as part of a phosphoryl shuttle between enzyme I and sugar-specific proteins of the PTS. HPr mediates crosstalk between PTS sugar uptake and glycogen breakdown. The evolution of the allosteric regulation of E. coli GP by HPr is compared to that of other phosphorylases.
Abstract
This study evaluated the 5-year clinical outcomes of the Genoss DES, the first Korean-made sirolimus-eluting coronary stent with abluminal biodegradable polymer.
We previously conducted the ...first-in-patient prospective, multicenter, randomized trial with a 1:1 ratio of patients using the Genoss DES and Promus Element stents; the angiographic and clinical outcomes of the Genoss DES stent were comparable to those of the Promus Element stent. The primary endpoint was major adverse cardiac events (MACE), which was a composite of death, myocardial infarction (MI), and target lesion revascularization (TLR) at 5 years.
We enrolled 38 patients in the Genoss DES group and 39 in the Promus Element group. Thirty-eight patients (100%) from the Genoss DES group and 38 (97.4%) from the Promus Element group were followed up at 5 years. The rates of MACE (5.3% vs 12.8%,
P
= .431), death (5.3% vs 10.3%,
P
= .675), TLR (2.6% vs 2.6%,
P
= 1.000), and target vessel revascularization (TVR) (7.9% vs 2.6%,
P
= .358) at 5 years did not differ significantly between the groups. No TLR or target vessel revascularization was reported from years 1 to 5 after the index procedure, and no MI or stent thrombosis occurred in either group during 5 years.
The biodegradable polymer Genoss DES and durable polymer Promus Element stents showed comparable low rates of MACE at the 5-year clinical follow-up.
Small hepatic masses often do not have distinct margins on B-mode EUS images. Contrast-enhanced harmonic EUS (CEH-EUS) is widely used for evaluating ambiguous pancreatic lesions. However, its role in ...detecting hepatic lesions and the use of EUS-guided FNA are not well evaluated. We investigated the usefulness of CEH-EUS–guided FNA for evaluating hepatic lesions.
Thirty consecutive patients with hepatic masses underwent CEH-EUS and CEH-EUS–guided FNA between September 2010 and November 2016.
Twenty-eight patients (93.3%) had malignant tumors and 2 patients (6.7%) had benign hepatic masses. Before contrast enhancement, 73.3% of the hepatic lesions (22/30) in the patient cohort were visible on B mode. After contrast enhancement, 93.3% of these hepatic lesions (28/30) were distinguishable from the surrounding liver parenchyma. The technical success rate was 100%. The median tumor size on EUS and the number of needle passes were 24.5 mm (interquartile range IQR, 14.5-40.8) and 2 (IQR, 2-3), respectively. The diagnostic accuracy of CEH-EUS–guided FNA was 86.7% (26/30 cases). There were no procedure-related adverse events.
CEH-EUS–guided FNA can be a safe and efficient method for the diagnosis of hepatic masses. It can result in high diagnostic accuracy in cases where the hepatic lesions are poorly visible on conventional EUS.
A stable and robust trypsin-based biocatalytic system was developed and demonstrated for proteomic applications. The system utilizes polymer nanofibers coated with trypsin aggregates for immobilized ...protease digestions. After covalently attaching an initial layer of trypsin to the polymer nanofibers, highly concentrated trypsin molecules are crosslinked to the layered trypsin by way of a glutaraldehyde treatment. This process produced a 300-fold increase in trypsin activity compared with a conventional method for covalent trypsin immobilization, and proved to be robust in that it still maintained a high level of activity after a year of repeated recycling. This highly stable form of immobilized trypsin was resistant to autolysis, enabling repeated digestions of BSA over 40 days and successful peptide identification by LC-MS/MS. This active and stable form of immobilized trypsin was successfully employed in the digestion of yeast proteome extract with high reproducibility and within shorter time than conventional protein digestion using solution phase trypsin. Finally, the immobilized trypsin was resistant to proteolysis when exposed to other enzymes (i.e., chymotrypsin), which makes it suitable for use in "real-world" proteomic applications. Overall, the biocatalytic nanofibers with trypsin aggregate coatings proved to be an effective approach for repeated and automated protein digestion in proteomic analyses.
Meso-structured onion-like silica (Meso-Onion-S) was synthesized and used as a host of enzyme immobilization. Meso-Onion-S has a 200–300 nm sized primary meso-structured onion building unit, and each ...onion unit has highly curved mesopores of 10 nm diameter in a multishell structure. Nanoscale enzyme reactors (NERs) in Meso-Onion-S were prepared via a two-step process of enzyme adsorption and subsequent enzyme cross-linking, which effectively prevents the leaching of cross-linked enzyme aggregates from highly curved mesopores of Meso-Onion-S. As a result, NERs in Meso-Onion-S significantly improved the enzyme stability as well as the enzyme loading. For example, NER of lipase (NER-LP) was stable under rigorous shaking for 40 days, while the control sample of adsorbed LP (ADS-LP) with no enzyme cross-linking showed a rapid inactivation due to rigorous enzyme leaching under shaking. Stable NER-LP was successfully employed to produce biodiesels and fatty acid methyl esters, from the LP-catalyzed transesterification of soybean oil with methanol. Interestingly, the specific activity of NER-LP was 23 and 10 times higher than those of free LP and ADS-LP, respectively, revealing the importance of LP stabilization in the form of NER-LP in the presence of organic solvents.
PDF
