scholarly journals GTPase mechanism and function: new insights from systematic mutational analysis of the phosphate-binding loop residue Ala30 of Rab5

2000 ◽  
Vol 346 (2) ◽  
pp. 501-508 ◽  
Author(s):  
Zhimin LIANG ◽  
Timothy MATHER ◽  
Guangpu LI
Keyword(s):  
Biological Activity ◽  
Mutational Analysis ◽  
The Other ◽  
Hydrolysis Reaction ◽  
Rab Gtpase ◽  
Gtpase Activity ◽  
Phosphate Binding ◽  
Gtp Hydrolysis ◽  
Arginine Residues ◽  
Binding Loop

Structural and biochemical data indicate the importance of the phosphate-binding loop residues Gly12 and Gly13 of Ras both in the GTP hydrolysis reaction and in biological activity, but these two residues are not conserved in other Ras-related GTPases. To gain a better understanding of this region in GTP hydrolysis and GTPase function, we used the Ras-related Rab5 GTPase as a model for comparison, and substituted the Ala30 residue (the equivalent of Gly13 of Ras) with all the other 19 amino acids. The resulting mutants were analysed for GTP hydrolysis, GTP binding, GTP dissociation and biological activity. Only the substitution of alanine with proline reduced the GTPase activity by an order of magnitude. This effect is in sharp contrast with the observation that a proline substitution at the neighbouring position (Gly12 of Ras) has little effect on the GTPase activity. Whereas most other substitutions showed either a small negative effect or no effect on the GTPase activity, the arginine substitution surprisingly stimulated the GTPase activity by 5-fold. Molecular modelling suggests that this built-in arginine mimics the catalytic arginine residues found in trimeric GTPases and GTPase-activating proteins in providing the positive charge to facilitate the GTP hydrolysis reaction. We investigated further the biological activity of the Rab5 mutants in relation to stimulating endocytosis. When expressed in cultured baby hamster kidney cells, both arginine and proline mutants, like wild-type Rab5, stimulated endocytosis. However, the arginine mutant was a more potent stimulator than the proline mutant (3-fold stimulation as against 1.7-fold). The tryptophan mutant, on the other hand, was completely deficient in activity in terms of the stimulation of endocytosis, demonstrating the importance of the phosphate-binding loop in Rab GTPase function.

scholarly journals Mutational Analysis of the Phosphate-Binding Loop of Rhizobium meliloti DctD, a ς54-Dependent Activator

1998 ◽  
Vol 180 (10) ◽  
pp. 2792-2795 ◽  
Author(s):  
Yan Gao ◽  
Ying-Kai Wang ◽  
Timothy R. Hoover
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Atp Hydrolysis ◽  
Mutational Analysis ◽  
Rhizobium Meliloti ◽  
Atp Binding ◽  
Phosphate Binding ◽  
Binding Loop

ABSTRACT The phosphate-binding loop of ς54-dependent activators is thought to participate in ATP binding and/or hydrolysis. Alanine substitutions at positions 3, 4, 6, 7, and 8 of this motif inRhizobium meliloti DctD disrupted transcriptional activation and ATP hydrolysis. Interestingly, substitution of alanine at position 7 also affected DNA binding.

Elucidating Microscopic Events Driven by GTP Hydrolysis Reaction in Ras-GAP System with Semi-reactive Molecular Dynamics Simulation: Alternative Role of Phosphate Binding Loop as Mechanical Energy Storage

2021 ◽  
Author(s):  
Ikuo Kurisaki ◽  
Shigenori Tanaka
Keyword(s):  
Molecular Dynamics ◽  
Energy Storage ◽  
Molecular Dynamics Simulation ◽  
Mechanical Energy ◽  
Dynamics Simulation ◽  
Phosphate Binding ◽  
Gtp Hydrolysis ◽  
Reactive Molecular Dynamics ◽  
Binding Loop

ATPase and GTPase have been widely found as chemical energy-mechanical work transducers, whereas the physicochemical mechanisms are not satisfactorily understood. We addressed the problem by examining John Ross’ conjecture that...

scholarly journals Cooperative and Critical Roles for Both G Domains in the GTPase Activity and Cellular Function of Ribosome-Associated Escherichia coli EngA

2006 ◽  
Vol 188 (22) ◽  
pp. 7992-7996 ◽  
Author(s):  
Amrita Bharat ◽  
Mengxi Jiang ◽  
Susan M. Sullivan ◽  
Janine R. Maddock ◽  
Eric D. Brown
Keyword(s):  
Escherichia Coli ◽  
Ribosomal Subunit ◽  
Cellular Function ◽  
Gtpase Activity ◽  
Cellular Phenotype ◽  
Phosphate Binding ◽  
Biochemical Function ◽  
Polysome Profile ◽  
Binding Loop

ABSTRACT To probe the cellular phenotype and biochemical function associated with the G domains of Escherichia coli EngA (YfgK, Der), mutations were created in the phosphate binding loop of each. Neither an S16A nor an S217A variant of G domain 1 or 2, respectively, was able to support growth of an engA conditional null. Polysome profiles of EngA-depleted cells were significantly altered, and His6-EngA was found to cofractionate with the 50S ribosomal subunit. The variants were unable to complement the abnormal polysome profile and were furthermore significantly impacted with respect to in vitro GTPase activity. Together, these observations suggest that the G domains have a cooperative function in ribosome stability and/or biogenesis.

A FACILE SYNTHESIS AND REACTIONS OF AMINO SELENOLO[2,3-b]PYRIDINE CARBOXYLATE

2015 ◽  
Vol 12 (1) ◽  
pp. 3910-3918 ◽  
Author(s):  
Dr Remon M Zaki ◽  
Prof Adel M. Kamal El-Dean ◽  
Dr Nermin A Marzouk ◽  
Prof Jehan A Micky ◽  
Mrs Rasha H Ahmed
Keyword(s):  
Biological Activity ◽  
Carbonyl Compounds ◽  
Mass Spectra ◽  
The Other ◽  
Pyridine Derivatives ◽  
Facile Synthesis ◽  
High Biological Activity ◽  
Basic Hydrolysis ◽  
Pyridine Carboxylate ◽  
Hydrolysis Of

 Incorporating selenium metal bonded to the pyridine nucleus was achieved by the reaction of selenium metal with 2-chloropyridine carbonitrile 1 in the presence of sodium borohydride as reducing agent. The resulting non isolated selanyl sodium salt was subjected to react with various α-halogenated carbonyl compounds to afford the selenyl pyridine derivatives 3a-f  which compounds 3a-d underwent Thorpe-Ziegler cyclization to give 1-amino-2-substitutedselenolo[2,3-b]pyridine compounds 4a-d, while the other compounds 3e,f failed to be cyclized. Basic hydrolysis of amino selenolo[2,3-b]pyridine carboxylate 4a followed by decarboxylation furnished the corresponding amino selenolopyridine compound 6 which was used as a versatile precursor for synthesis of other heterocyclic compound 7-16. All the newly synthesized compounds were established by elemental and spectral analysis (IR, 1H NMR) in addition to mass spectra for some of them hoping these compounds afforded high biological activity.

Effect of C6-Volatiles on Bioluminescent Plant Pathogens

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 557d-557
Author(s):  
Jennifer Warr ◽  
Fenny Dane ◽  
Bob Ebel
Keyword(s):  
Biological Activity ◽  
Bacterial Growth ◽  
Xanthomonas Campestris ◽  
Plant Pathogens ◽  
Genetically Engineered ◽  
The Other ◽  
Computer Assisted ◽  
Signal Molecules ◽  
Low Concentrations

C6 volatile compounds are known to be produced by the plant upon pathogen attack or other stress-related events. The biological activity of many of these substances is poorly understood, but some might produce signal molecules important in host–pathogen interactions. In this research we explored the possibility that lipid-derived C6 volatiles have a direct effect on bacterial plant pathogens. To this purpose we used a unique tool, a bacterium genetically engineered to bioluminesce. Light-producing genes from a fish-associated bacterium were introduced into Xanthomonas campestris pv. campestris, enabling nondestructive detection of bacteria in vitro and in the plant with special computer-assisted camera equipment. The effects of different C6 volatiles (trans-2 hexanal, trans-2 hexen-1-ol and cis-3 hexenol) on growth of bioluminescent Xanthomonas campestris were investigated. Different volatile concentrations were used. Treatment with trans-2 hexanal appeared bactericidal at low concentrations (1% and 10%), while treatments with the other volatiles were not inhibitive to bacterial growth. The implications of these results with respect to practical use of trans-2 hexanal in pathogen susceptible and resistant plants will be discussed.

Intercalation Processes in Cobalt Substituted Nickel Oxyhydroxides

1990 ◽  
Vol 210 ◽  
Author(s):  
Claude Delmas
Keyword(s):  
Ir Spectroscopy ◽  
Mechanical Treatment ◽  
Positive Charge ◽  
Van Der Waals ◽  
The Other ◽  
Hydrolysis Reaction ◽  
Water Molecules ◽  
Layered Oxides ◽  
Experimental Conditions ◽  
Cobalt Ions

AbstractChimie douce reactions (hydrolysis and reduction) from layered oxides : NaNiO2, NaxCoO2 and NaNil-xCoxO2 lead to numerous oxyhydroxides and hydroxides which differ by the composition of the intersheet space.According to the experimental conditions of the hydrolysis reaction, the oxyhydroxides can be unhydrated or intercalated with one or two layers of water molecules. From the most hydrated phases, the other ones can be obtained by chemical, thermal and even mechanical treatment.The reduction of Co-substituted nickel oxyhydroxides leads to hydroxides in which nickel and cobalt ions are respectively divalent and trivalent. In order to compensate the excess of positive charge in the (Ni, Co)O2 sheet, anions (OH-, CO32-, SO42-, NO3-) are inserted in the Van der Waals gap.For the highest anion amounts, well ordered α*-type materials are obtained. Water molecules are simultaneously inserted in the interslab space. Their structure is strongly related to the hydrotalcite one. When the amouit of anions in the intersheet space is not sufficient, interstratified materials are obtained. In this case the (Ni,Co)(OH)2 slabs are separated by a layer of CO32- anions and water molecules (α*-type) or by an empty Van der Waals gap (β(II)-type). The amount of α*-type planes in the structure increases with the cobalt amount. All these materials have been characterized by IR spectroscopy which allows to detect the existence of two types of O-H bonds (free in α*-type plane or hydrogen bonded in ²(II)-type plane).

scholarly journals Isolasi dan Identifikasi Senyawa Fenolik dari Kulit Akar Tumbuhan Artocarpus Dadah Miq 63-74

2015 ◽  
Vol 4 (2) ◽  
pp. 205
Author(s):  
Indarto Indarto
Keyword(s):  
Biological Activity ◽  
Phenolic Compounds ◽  
Ir Spectroscopy ◽  
The Other ◽  
Flash Chromatography ◽  
Rare Plant ◽  
Isolation And Purification ◽  
Phenolic Group ◽  
The Village ◽  
Murine Leukemia

Artocarpus plant  dadah  Miq.  is one of the species of Artocarpus of the Moraceae family that belongs to a rare plant in nature. This plant is known as the main source of phenolic derivative compound that is flavone compound  in  or  tri-oxygenated and terisoprenilasi in C-3 position ,  and also known as the main source of phenolic compound derived flavonoids, aryl-benzofuran, stilbenoid and xanthane flavonoida, which have biological activity as promoters antitumor, antibacterial, antifungal, antiimflamatori, antikanker and others. This study aimed to isolate and identify the phenolic compounds contained in plant  A .  dadah obtained from the village of Purwoasri, North Metro District, Metro City, Lampung Province. Research stages include collection and sample preparation and extraction, isolation, and purification of compounds using KCV method, flash chromatography  , KKG, and TLC, while the identification of compounds is performed using ultraviolet-visible (UV-VIS) and infrared (IR) spectroscopy. In the present study, three compounds were isolated, one of which was estimated to be flavonoid compounds based on UV-VIS and IR spectra data which also had high activity against murine leukemia P-388 cells with IC 50  3.1 μg / mL. Based on the IR spectral data for the other two compounds there is a -OH uptake in the region of 3200-3500 cm -1, C = C aromatic uptake in the area of 1600-1400 cm -1 , so it is estimated that both compounds are phenolic group compounds.Tumbuhan Artocarpus dadah Miq.merupakan salah satu spesies Artocarpus dari famili Moraceae yang termasuk tumbuhan langka di alam. Tumbuhan ini dikenal sebagai sumber utama senyawa turunan fenolik yaitu senyawa flavon di atau tri-oksigenasi dan terisoprenilasi pada posisi C-3, dan juga dikenal sebagai sumber utama senyawa fenolik turunan flavonoid, aril-benzofuran, stilbenoid dan santon turunan flavonoida, yang memiliki aktivitas biologi sebagai promotor antitumor, antibakteri, antifungal, antiimflamatori, antikanker dan lain-lain.Penelitian ini bertujuan untuk mengisolasi dan mengidentifikasi senyawa fenolik yang terkandung dalam tumbuhan A. dadah yang diperoleh dari desa Purwoasri, Kecamatan Metro Utara, Kota Metro, Provinsi Lampung.Tahapan penelitian yang dilakukan meliputi pengumpulan dan persiapan sampel kemudian ekstraksi, isolasi, dan pemurnian senyawa menggunakan metode KCV, kromatografi flash, KKG, dan KLT, sedangkan identifikasi senyawa dilakukan menggunakan spektroskopi ultraungu-tampak (UV-VIS) dan inframerah (IR). Pada penelitian ini telah berhasil diisolasi tiga senyawa, yang salah satunya diperkirakan senyawa flavonoid berdasarkan data spektrum UV-VIS dan IR yang juga memiliki aktivitas tinggi terhadap sel murine leukemia P-388 dengan IC50 3,1 μg/mL. Berdasarkan data spektrum IR untuk dua senyawa yang lain terdapat serapan –OH pada daerah 3200-3500 cm-1, serapan C=C aromatik di daerah 1600-1400 cm-1, sehingga diperkirakan kedua senyawa tersebut merupakan senyawa golongan fenolik.

scholarly journals FlhF and Its GTPase Activity Are Required for Distinct Processes in Flagellar Gene Regulation and Biosynthesis in Campylobacter jejuni

2009 ◽  
Vol 191 (21) ◽  
pp. 6602-6611 ◽  
Author(s):  
Murat Balaban ◽  
Stephanie N. Joslin ◽  
David R. Hendrixson
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Campylobacter Jejuni ◽  
Regulatory System ◽  
Flagellar Gene ◽  
Gtpase Activity ◽  
Gtp Hydrolysis ◽  
Genetic Analyses ◽  
Flagellar Biosynthesis ◽  
Two Component

ABSTRACT FlhF proteins are putative GTPases that are often necessary for one or more steps in flagellar organelle development in polarly flagellated bacteria. In Campylobacter jejuni, FlhF is required for σ54-dependent flagellar gene expression and flagellar biosynthesis, but how FlhF influences these processes is unknown. Furthermore, the GTPase activity of any FlhF protein and the requirement of this speculated activity for steps in flagellar biosynthesis remain uncharacterized. We show here that C. jejuni FlhF hydrolyzes GTP, indicating that these proteins are GTPases. C. jejuni mutants producing FlhF proteins with reduced GTPase activity were not severely defective for σ54-dependent flagellar gene expression, unlike a mutant lacking FlhF. Instead, these mutants had a propensity to lack flagella or produce flagella in improper numbers or at nonpolar locations, indicating that GTP hydrolysis by FlhF is required for proper flagellar biosynthesis. Additional studies focused on elucidating a possible role for FlhF in σ54-dependent flagellar gene expression were conducted. These studies revealed that FlhF does not influence production of or signaling between the flagellar export apparatus and the FlgSR two-component regulatory system to activate σ54. Instead, our data suggest that FlhF functions in an independent pathway that converges with or works downstream of the flagellar export apparatus-FlgSR pathway to influence σ54-dependent gene expression. This study provides corroborative biochemical and genetic analyses suggesting that different activities of the C. jejuni FlhF GTPase are required for distinct steps in flagellar gene expression and biosynthesis. Our findings are likely applicable to many polarly flagellated bacteria that utilize FlhF in flagellar biosynthesis processes.

Thyroxine, liothyronine and thyroid BP

1964 ◽  
Vol 2 (6) ◽  
pp. 21-22
Keyword(s):  
Biological Activity ◽  
The Other ◽  
Pure Substance ◽  
British Pharmacopoeia ◽  
Chemical Assay

L-thyroxine (Eltroxin - Glaxo; and others), liothyronine (Tertroxin - Glaxo; and others), a mixture of l-thyroxine and l-triiodothyronine (Diotroxin - Glaxo) and dried thyroid (Thyroid BP) are all used in the management of hypothyroidism. Large quantities of Thyroid BP are unfortunately still prescribed, probably not all for the treatment of demonstrable hypothyroidism. Unlike the other preparations, it is not a pure substance and needs to be assayed biologically. Chemical assay which is required by the British Pharmacopoeia does not reflect comparable biological activity.

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