Intercalation of triethylphosphine oxide bearing a phosphoryl group into Dion–Jacobson-type ion-exchangeable layered perovskites

2015 ◽  
Vol 44 (7) ◽  
pp. 3002-3008 ◽  
Author(s):  
Nagisa Toihara ◽  
Yoriyoshi Yoneyama ◽  
Akira Shimada ◽  
Seiichi Tahara ◽  
Yoshiyuki Sugahara
Keyword(s):  
Phosphoryl Group ◽  
Triethylphosphine Oxide ◽  
Hydrolysis Of ◽  
Layered Perovskites

Triethylphosphine oxide [(C2H5)3PO; TEPO] was intercalated into protonated Dion–Jacobson-type ion-exchangeable layered perovskites, HLaNb2O7·xH2O and HCa2Nb3O10·xH2O, by hydrolysis of their n-decoxy derivatives in the presence of TEPO.

Inhibitors of Serine/Threonine Protein Phosphatases: Biochemical and Structural Studies Provide Insight for Further Development

2019 ◽  
Vol 26 (15) ◽  
pp. 2634-2660 ◽  
Author(s):  
Mark R. Swingle ◽  
Richard E. Honkanen
Keyword(s):  
Protein Kinases ◽  
Catalytic Mechanism ◽  
Protein Phosphatases ◽  
Phosphoryl Group ◽  
Structural Studies ◽  
Reversible Phosphorylation ◽  
Natural Toxins ◽  
Rate Of Hydrolysis ◽  
Further Development ◽  
Hydrolysis Of

Background:The reversible phosphorylation of proteins regulates many key functions in eukaryotic cells. Phosphorylation is catalyzed by protein kinases, with the majority of phosphorylation occurring on side chains of serine and threonine residues. The phosphomonoesters generated by protein kinases are hydrolyzed by protein phosphatases. In the absence of a phosphatase, the half-time for the hydrolysis of alkyl phosphate dianions at 25º C is over 1 trillion years; knon ~2 x 10-20 sec-1. Therefore, ser/thr phosphatases are critical for processes controlled by reversible phosphorylation.Methods:This review is based on the literature searched in available databases. We compare the catalytic mechanism of PPP-family phosphatases (PPPases) and the interactions of inhibitors that target these enzymes.Results:PPPases are metal-dependent hydrolases that enhance the rate of hydrolysis ([kcat/kM]/knon ) by a factor of ~1021, placing them among the most powerful known catalysts on earth. Biochemical and structural studies indicate that the remarkable catalytic proficiencies of PPPases are achieved by 10 conserved amino acids, DXH(X)~26DXXDR(X)~20- 26NH(X)~50H(X)~25-45R(X)~30-40H. Six act as metal-coordinating residues. Four position and orient the substrate phosphate. Together, two metal ions and the 10 catalytic residues position the phosphoryl group and an activated bridging water/hydroxide nucleophile for an inline attack upon the substrate phosphorous atom. The PPPases are conserved among species, and many structurally diverse natural toxins co-evolved to target these enzymes.Conclusion:Although the catalytic site is conserved, opportunities for the development of selective inhibitors of this important group of metalloenzymes exist.

scholarly journals Hydrolysis of GTP by Sec4 protein plays an important role in vesicular transport and is stimulated by a GTPase-activating protein in Saccharomyces cerevisiae.

1992 ◽  
Vol 12 (5) ◽  
pp. 2017-2028 ◽  
Author(s):  
N C Walworth ◽  
P Brennwald ◽  
A K Kabcenell ◽  
M Garrett ◽  
P Novick
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Synthetic Lethality ◽  
Vesicular Transport ◽  
Yeast Cells ◽  
Hydrolysis Rate ◽  
Phosphoryl Group ◽  
Absolute Level ◽  
Yeast Saccharomyces Cerevisiae ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Sec4, a GTP-binding protein of the ras superfamily, is required for exocytosis in the budding yeast Saccharomyces cerevisiae. To test the role of GTP hydrolysis in Sec4 function, we constructed a mutation, Q-79----L, analogous to the oncogenic mutation of Q-61----L in Ras, in a region of Sec4 predicted to interact with the phosphoryl group of GTP. The sec4-leu79 mutation lowers the intrinsic hydrolysis rate to unmeasurable levels. A component of a yeast lysate specifically stimulates the hydrolysis of GTP by Sec4, while the rate of hydrolysis of GTP by Sec4-Leu79 can be stimulated by this GAP activity to only 30% of the stimulated hydrolysis rate of the wild-type protein. The decreased rate of hydrolysis results in the accumulation of the Sec4-Leu79 protein in its GTP-bound form in an overproducing yeast strain. The sec4-leu79 allele can function as the sole copy of sec4 in yeast cells. However, it causes recessive, cold-sensitive growth, a slowing of invertase secretion, and accumulation of secretory vesicles and displays synthetic lethality with a subset of other secretory mutants, indicative of a partial loss of Sec4 function. While the level of Ras function reflects the absolute level of GTP-bound protein, our results suggest that the ability of Sec4 to cycle between its GTP and GDP bound forms is important for its function in vesicular transport, supporting a mechanism for Sec4 function which is distinct from that of the Ras protein.

Hydrolysis of GTP by Sec4 protein plays an important role in vesicular transport and is stimulated by a GTPase-activating protein in Saccharomyces cerevisiae

1992 ◽  
Vol 12 (5) ◽  
pp. 2017-2028
Author(s):  
N C Walworth ◽  
P Brennwald ◽  
A K Kabcenell ◽  
M Garrett ◽  
P Novick
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Synthetic Lethality ◽  
Vesicular Transport ◽  
Yeast Cells ◽  
Hydrolysis Rate ◽  
Phosphoryl Group ◽  
Absolute Level ◽  
Yeast Saccharomyces Cerevisiae ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Sec4, a GTP-binding protein of the ras superfamily, is required for exocytosis in the budding yeast Saccharomyces cerevisiae. To test the role of GTP hydrolysis in Sec4 function, we constructed a mutation, Q-79----L, analogous to the oncogenic mutation of Q-61----L in Ras, in a region of Sec4 predicted to interact with the phosphoryl group of GTP. The sec4-leu79 mutation lowers the intrinsic hydrolysis rate to unmeasurable levels. A component of a yeast lysate specifically stimulates the hydrolysis of GTP by Sec4, while the rate of hydrolysis of GTP by Sec4-Leu79 can be stimulated by this GAP activity to only 30% of the stimulated hydrolysis rate of the wild-type protein. The decreased rate of hydrolysis results in the accumulation of the Sec4-Leu79 protein in its GTP-bound form in an overproducing yeast strain. The sec4-leu79 allele can function as the sole copy of sec4 in yeast cells. However, it causes recessive, cold-sensitive growth, a slowing of invertase secretion, and accumulation of secretory vesicles and displays synthetic lethality with a subset of other secretory mutants, indicative of a partial loss of Sec4 function. While the level of Ras function reflects the absolute level of GTP-bound protein, our results suggest that the ability of Sec4 to cycle between its GTP and GDP bound forms is important for its function in vesicular transport, supporting a mechanism for Sec4 function which is distinct from that of the Ras protein.

Photoinactivation of the Staphylococcus aureus Lactose-Specific EIICB Phosphotransferase Component with p-azidophenyl-β-D-Galactoside and Phosphorylation of the Covalently Bound Substrate

2018 ◽  
Vol 28 (3) ◽  
pp. 147-158
Author(s):  
Gina Sossna-Wunder ◽  
Wolfgang Hengstenberg ◽  
Pierre Briozzo ◽  
Josef Deutscher
Keyword(s):  
Staphylococcus Aureus ◽  
Sequence Data ◽  
Uv Light ◽  
Acid Resistance ◽  
Binding Pocket ◽  
Phosphoryl Group ◽  
Phosphotransferase System ◽  
Substrate Binding Pocket ◽  
Hydrolysis Of ◽  
Covalently Bound

<b><i>Background:</i></b> The phosphoenolpyruvate (PEP):lactose phosphotransferase system of<i> Staphylococcus aureus</i> transports and phosphorylates lactose and various phenylgalactosides. Their phosphorylation is catalyzed by the Cys476-phosphorylated EIIB domain of the lactose-specific permease enzyme IICB (EIICB<sup>Lac</sup>). Phosphorylation causes the release of galactosides bound to the EIIC domain into the cytoplasm by a mechanism not yet understood. <b><i>Results:</i></b> Irradiation of a reaction mixture containing the photoactivatable <i>p</i>-azidophenyl-β-D-galactopyranoside and EIICB<sup>Lac</sup> with UV light caused a loss of EIICB<sup>Lac</sup> activity. Nevertheless, photoinactivated EIICB<sup>Lac</sup> could still be phosphorylated with [<sup>32</sup>P]PEP. Proteolysis of photoinactivated [<sup>32</sup>P]P-EIICB<sup>Lac</sup> with subtilisin provided an 11-kDa radioactive peptide. Only the sequence of its first three amino acids (-H-G-P-, position 245–247) could be determined. They are part of the substrate binding pocket in EIICs of the lactose/cellobiose PTS family. Surprisingly, while acid treatment caused hydrolysis of the phosphoryl group in active [<sup>32</sup>P]P∼EIICB<sup>Lac</sup>, photoinactivated [<sup>32</sup>P]P-EIICB<sup>Lac</sup> remained strongly phosphorylated. <b><i>Conclusion:</i></b> Phosphorylation of the –OH group at C6 of <i>p</i>-nitrenephenyl-β-D-galactopyranoside covalently bound to EIIC<sup>Lac</sup> by the histidyl-phosphorylated [<sup>32</sup>P]P∼EIIB<sup>Lac</sup> domain is a likely explanation for the observed acid resistance. Placing <i>p</i>-nitrenephenyl-β-D-galactopyranoside into the active site of modelled EIIC<sup>Lac</sup> suggested that the nitrene binds to the -NH- group of Ser248, which would explain why no sequence data beyond Pro247could be obtained.

Fine Structural Localization of Acyltransferases Involved in Lipid Synthesis in Intestinal Mucosa.

1970 ◽  
Vol 28 ◽  
pp. 54-55
Author(s):  
R. J. Barrnett ◽  
J. A. Higgins
Keyword(s):  
Smooth Endoplasmic Reticulum ◽  
Lipid Synthesis ◽  
Mucosal Cell ◽  
Structural Localization ◽  
Morphological Studies ◽  
Mucosal Cells ◽  
Initial Appearance ◽  
Sh Group ◽  
Hydrolysis Of ◽  
Intestinal Mucosal Cells

The main products of intestinal hydrolysis of dietary triglycerides are free fatty acids and monoglycerides. These form micelles from which the lipids are absorbed across the mucosal cell brush border. Biochemical studies have indicated that intestinal mucosal cells possess a triglyceride synthesising system, which uses monoglyceride directly as an acylacceptor as well as the system found in other tissues in which alphaglycerophosphate is the acylacceptor. The former pathway is used preferentially for the resynthesis of triglyceride from absorbed lipid, while the latter is used mainly for phospholipid synthesis. Both lipids are incorporated into chylomicrons. Morphological studies have shown that during fat absorption there is an initial appearance of fat droplets within the cisternae of the smooth endoplasmic reticulum and that these subsequently accumulate in the golgi elements from which they are released at the lateral borders of the cell as chylomicrons.We have recently developed several methods for the fine structural localization of acyltransferases dependent on the precipitation, in an electron dense form, of CoA released during the transfer of the acyl group to an acceptor, and have now applied these methods to a study of the fine structural localization of the enzymes involved in chylomicron lipid biosynthesis. These methods are based on the reduction of ferricyanide ions by the free SH group of CoA.

Lattice imaging and pore structure of β ferric oxyhydroxide

1978 ◽  
Vol 36 (1) ◽  
pp. 264-265
Author(s):  
T. Baird ◽  
J.R. Fryer ◽  
S.T. Galbraith
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bulk Material ◽  
Model Structure ◽  
Bulk Crystals ◽  
Lattice Imaging ◽  
Thin Sections ◽  
Ferric Oxyhydroxide ◽  
Resolution Electron ◽  
Hydrolysis Of

Introduction Previously we had suggested (l) that the striations observed in the pod shaped crystals of β FeOOH were an artefact of imaging in the electron microscope. Contrary to this adsorption measurements on bulk material had indicated the presence of some porosity and Gallagher (2) had proposed a model structure - based on the hollandite structure - showing the hollandite rods forming the sides of 30Å pores running the length of the crystal. Low resolution electron microscopy by Watson (3) on sectioned crystals embedded in methylmethacrylate had tended to support the existence of such pores.We have applied modern high resolution techniques to the bulk crystals and thin sections of them without confirming these earlier postulatesExperimental β FeOOH was prepared by room temperature hydrolysis of 0.01M solutions of FeCl3.6H2O, The precipitate was washed, dried in air, and embedded in Scandiplast resin. The sections were out on an LKB III Ultramicrotome to a thickness of about 500Å.

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