scholarly journals Synthesis and Biochemical Studies of 19-Oxygenated Derivatives of 6.ALPHA.- and 6.BETA.-Methylandrostenediones as Catalytic Probes for the Active Site of Aromatase.

2000 ◽  
Vol 23 (9) ◽  
pp. 1059-1065 ◽  
Author(s):  
Mitsuteru NUMAZAWA ◽  
Akiko YOSHIMURA
Keyword(s):  
Active Site ◽  
Biochemical Studies ◽  
Derivatives Of

Acyl-Enzymes as Thrombolytic Agents in Dog Models of Venous Thrombosis and Pulmonary Embolism

1984 ◽  
Vol 51 (02) ◽  
pp. 248-253 ◽  
Author(s):  
R J Dupe ◽  
P D English ◽  
R A G Smith ◽  
J Green
Keyword(s):  
Pulmonary Embolism ◽  
Side Effects ◽  
Venous Thrombosis ◽  
Active Site ◽  
Acute Pulmonary Embolism ◽  
Quantitative Model ◽  
Beagle Dog ◽  
Thrombosis Model ◽  
Derivatives Of

SummaryA quantitative model of venous thrombosis in the beagle dog is described. The model was adapted to permit ageing of isolated experimental clots in vivo. A model of acute pulmonary embolism in this species is also described. In the venous thrombosis model, infusion of streptokinase (SK) or SK-activated human plasmin gave significant lysis but bolus doses of SK. plasmin complex were ineffective. Active site anisoylated derivatives of SK. plasminogen complex, SK-activated plasmin and activator-free plasmin were all active when given as bolus doses in both models. At lytic doses, the acyl-enzymes caused fewer side-effects attributable to plasminaemia than the corresponding unmodified enzymes.

The melanocyte stimulating activity of N-nitroso-2-chloroethyl-carbamoyl derivatives of α-melanotropin fragments

1988 ◽  
Vol 53 (11) ◽  
pp. 2574-2582 ◽  
Author(s):  
Hedvig Medzihradszky-Schweiger ◽  
Helga Süli-Vargha ◽  
József Bódi ◽  
Kálmán Medzihradszky
Keyword(s):  
Biological Activity ◽  
Active Site ◽  
Frog Skin ◽  
Terminal Sequence ◽  
Subsequent Reaction ◽  
Affinity Labels ◽  
Derivatives Of

A number of N-nitroso-2-chloroethyl-carbamoyl (Q(NO)) derivatives of α-melanotropin fragments have been synthesized and their effect on the frog skin melanocytes studied. Peptides substituted in this way possess the biological activity of the parent compounds, indicating that they preserved their receptor recognizing ability. These compounds can therefore serve as affinity labels. Some of these derivatives, related to the C-terminal sequence of α-melanotropin show prolonged darkening reaction, which does not influence the subsequent reaction of melanocytes with α-melanotropin. The Q(NO)-derivative of a fragment derived from the classical active site of the hormone shows, however, inhibition of the effect of α-melanotropin. It can be concluded that the latter peptide acts through the melanotropin receptor, while others, related to the C-terminal sequence of the hormone through another mechanism.

scholarly journals The structure of the RCAN1:CN complex explains the inhibition of and substrate recruitment by calcineurin

2020 ◽  
Vol 6 (27) ◽  
pp. eaba3681
Author(s):  
Yang Li ◽  
Sarah R. Sheftic ◽  
Simina Grigoriu ◽  
Charles D. Schwieters ◽  
Rebecca Page ◽  
...  
Keyword(s):  
Posttranslational Modifications ◽  
Active Site ◽  
Neurological Disorders ◽  
Critical Factor ◽  
Endogenous Inhibitor ◽  
Weak Inhibitor ◽  
Road Map ◽  
Biochemical Studies ◽  
Specific Manner ◽  
Multiple Routes

Regulator of calcineurin 1 (RCAN1) is an endogenous inhibitor of the Ser/Thr phosphatase calcineurin (CN). It has been shown that excessive inhibition of CN is a critical factor for Down syndrome and Alzheimer’s disease. Here, we determined RCAN1’s mode of action. Using a combination of structural, biophysical, and biochemical studies, we show that RCAN1 inhibits CN via multiple routes: first, by blocking essential substrate recruitment sites and, second, by blocking the CN active site using two distinct mechanisms. We also show that phosphorylation either inhibits RCAN1-CN assembly or converts RCAN1 into a weak inhibitor, which can be reversed by CN via dephosphorylation. This highlights the interplay between posttranslational modifications in regulating CN activity. Last, this work advances our understanding of how active site inhibition of CN can be achieved in a highly specific manner. Together, these data provide the necessary road map for targeting multiple neurological disorders.

ACTIVE SITE-SELECTIVE LABELING OF THROMBIN WITH FLUORESCENCE PROBES USING THI0ESTER DERIVATIVES OF PEPTIDE-CHL0R0METHYL KETONES

1987 ◽  
Author(s):  
Paul E Bock
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Thiol Group ◽  
Fluorescence Probes ◽  
Red Cross ◽  
Chloromethyl Ketone ◽  
Human Thrombin ◽  
Reaction Stoichiometry ◽  
Site Selective ◽  
Derivatives Of

Active site-directed inactivation of a serine protease with a thioester derivative of a peptide-chloromethyl ketone followed by reaction of the unique thiol group generatedin the presence of hydroxylamine with a fluorophore-iodoacetamide hasbeen investigated as a new method for covalent incorporation of extrinsic fluorescence probes into the active sites of blood coagulation proteases. The specificity of labeling by this method was evaluated by quantitation of the reactions between human thrombin, acetylthioacetyl-D-Phe-Pro-ArgCH2Cl (ATA-FPRCK) and 5-iodoacetamidofluorescein(IAF).ATA-FPRCK was synthesized by reaction of FPRCK with succinimidylacetylthioacetate and purified by chromatography on SP-Sephadex and Sephadex G10. Titrations of the loss of thrombin chromogenic substrate activity with ATA-FPRCK were linear, with end points of 1.1-1.2 mol ATA-FPRCK added/mol active sites, consistent with a reaction stoichiometry of 1 and the ∽90% purity of the compound estimated by reverse-phase HPLC.Inactivation of thrombin wasquantitatively correlated with incorporation of the thioester, with a maximum of 1.04 mol/mol active sites.IAF labeling of ATA-FPR-thrombin inthe presence of 0.1M NH20H yielded a maximu of 0.96 mol IAF incorporated/mol active sites in a reaction accompanied by loss of the thiol group. Incorporation of ATA-FPRCK wasdependent on thefunctional thrombin active site, asdemonstrated by less than 4%thioester or IAF incorporation for the enzyme previously inactivated with FPRCK. I conclude that active site-selective fluorescence labelingcan be achieved by the method described here with the advantage of a wide choice in the properties of theprobe incorporated. In addition, a 2.3-fold difference in fluorescenceintensity was observed for 2,6-ANS derivatives of ATA-FPR-thrombin andATA-D-Phe-Phe-Arg-thrombin, indicating that the spectral properties ofenvironmentally sensitive fluorescence probes are influenced by the structure of the peptide inhibitor.Supported in part by a grant from the American National Red Cross.

scholarly journals Albino mutants of Streptomyces glaucescens tyrosinase

1991 ◽  
Vol 274 (3) ◽  
pp. 707-713 ◽  
Author(s):  
M P Jackman ◽  
A Hajnal ◽  
K Lerch
Keyword(s):  
Active Site ◽  
Critical Role ◽  
Site Directed Mutagenesis ◽  
Mutant Proteins ◽  
Carbonyl Derivatives ◽  
Hydrogen Bonding Interactions ◽  
Albino Phenotype ◽  
Derivatives Of ◽  
Streptomyces Glaucescens

Site-directed mutagenesis was used to determine the functional role of several residues of Streptomyces glaucescens tyrosinase. Replacement of His-37, -53, -193 or -215 by glutamine yields albino phenotypes, as determined by expression on melanin-indicator plates. The purified mutant proteins display no detectable oxy-enzyme and increased Cu lability at the binuclear active site. The carbonyl derivatives of H189Q and H193Q luminesce, with lambda max. displaced more than 25 nm to a longer wavelength compared with native tyrosinase. The remaining histidine mutants display no detectable luminescence. The results are consistent with these histidine residues (together with His-62 and His-189 reported earlier) acting as Cu ligands in the Streptomyces glaucescens enzyme. Conservative substitution of the invariant Asn-190 by glutamine also gives an albino phenotype, no detectable oxy-enzyme and labilization of active-site Cu. The luminescence spectrum of carbonyl-N190Q, however, closely resembles that of the native enzyme under conditions promoting double Cu occupancy of the catalytic site. A critical role for Asn-190 in active-site hydrogen-bonding interactions is proposed.

scholarly journals Protein Engineering of Toluene-o-Xylene Monooxygenase from Pseudomonas stutzeri OX1 for Synthesizing 4-Methylresorcinol, Methylhydroquinone, and Pyrogallol

2004 ◽  
Vol 70 (6) ◽  
pp. 3253-3262 ◽  
Author(s):  
G�n�l Vardar ◽  
Thomas K. Wood
Keyword(s):  
Active Site ◽  
High Performance ◽  
Agar Plate ◽  
Pseudomonas Stutzeri ◽  
Saturation Mutagenesis ◽  
Dna Shuffling ◽  
Natural Substrate ◽  
Wild Type ◽  
Active Site Residues ◽  
Derivatives Of

ABSTRACT Toluene-o-xylene monooxygenase (ToMO) from Pseudomonas stutzeri OX1 oxidizes toluene to 3- and 4-methylcatechol and oxidizes benzene to form phenol; in this study ToMO was found to also form catechol and 1,2,3-trihydroxybenzene (1,2,3-THB) from phenol. To synthesize novel dihydroxy and trihydroxy derivatives of benzene and toluene, DNA shuffling of the alpha-hydroxylase fragment of ToMO (TouA) and saturation mutagenesis of the TouA active site residues I100, Q141, T201, and F205 were used to generate random mutants. The mutants were initially identified by screening with a rapid agar plate assay and then were examined further by high-performance liquid chromatography and gas chromatography. Several regiospecific mutants with high rates of activity were identified; for example, Escherichia coli TG1/pBS(Kan)ToMO expressing the F205G TouA saturation mutagenesis variant formed 4-methylresorcinol (0.78 nmol/min/mg of protein), 3-methylcatechol (0.25 nmol/min/mg of protein), and methylhydroquinone (0.088 nmol/min/mg of protein) from o-cresol, whereas wild-type ToMO formed only 3-methylcatechol (1.1 nmol/min/mg of protein). From o-cresol, the I100Q saturation mutagenesis mutant and the M180T/E284G DNA shuffling mutant formed methylhydroquinone (0.50 and 0.19 nmol/min/mg of protein, respectively) and 3-methylcatechol (0.49 and 1.5 nmol/min/mg of protein, respectively). The F205G mutant formed catechol (0.52 nmol/min/mg of protein), resorcinol (0.090 nmol/min/mg of protein), and hydroquinone (0.070 nmol/min/mg of protein) from phenol, whereas wild-type ToMO formed only catechol (1.5 nmol/min/mg of protein). Both the I100Q mutant and the M180T/E284G mutant formed hydroquinone (1.2 and 0.040 nmol/min/mg of protein, respectively) and catechol (0.28 and 2.0 nmol/min/mg of protein, respectively) from phenol. Dihydroxybenzenes were further oxidized to trihydroxybenzenes with different regiospecificities; for example, the I100Q mutant formed 1,2,4-THB from catechol, whereas wild-type ToMO formed 1,2,3-THB (pyrogallol). Regiospecific oxidation of the natural substrate toluene was also checked; for example, the I100Q mutant formed 22% o-cresol, 44% m-cresol, and 34% p-cresol, whereas wild-type ToMO formed 32% o-cresol, 21% m-cresol, and 47% p-cresol.

scholarly journals Reconstitution of Cu2+-depleted bovine serum amine oxidase with Co2+*

1998 ◽  
Vol 330 (1) ◽  
pp. 383-387 ◽  
Author(s):  
Enzo AGOSTINELLI ◽  
Giovanna DE MATTEIS ◽  
Bruno MONDOVÌ ◽  
Laura MORPURGO
Keyword(s):  
Active Site ◽  
Bovine Serum ◽  
Oxidase Activity ◽  
Amine Oxidase ◽  
Semiquinone Radical ◽  
Copper Site ◽  
Benzylamine Oxidase ◽  
Topa Quinone ◽  
Derivatives Of ◽  
Active Subunits

Two different Cu2+-depleted derivatives of bovine serum amine oxidase (BSAO) have recently been prepared, which contain about 0.5 mol/dimer of phenylhydrazine-reactive topa quinone (TPQ) cofactor and, depending on the reagents used, about 0.2 or 0.7 residual Cu2+/dimer [Agostinelli, De Matteis, Sinibaldi, Mondovì and Morpurgo (1997) Biochem. J. 324, 497-501]. The benzylamine oxidase activity of both derivatives was < 5% and increased up to ≈ 20% on incorporation of Co2+, irrespective of the residual Cu2+ content, which was unaffected by the treatment according to atomic absorption and ESR spectroscopy. The residual Cu2+ ions appeared to be distributed one per dimer and to be bound to inactive subunits, whereas Co2+ was bound to active subunits. The change in the active site had an appreciable influence on the kinetic behaviour. With several amines, the kinetic parameters, Km and kc, measured for Co2+-BSAO were different from those for native BSAO. This excludes the possibility that the catalytic activity was due to residual Cu2+. Furthermore, Co2+ restored to nearly native level the intensity of the TPQ 480 nm band and the reactions with phenylhydrazine or benzylhydrazine, which had been slowed down or abolished, respectively, in Cu2+-depleted samples. The CD spectrum, measured for the derivative with low Cu2+ content, was compatible with Co2+ binding to the copper site. The amine oxidase activity of the Co2+ derivative, which cannot form a semiquinone radical as an intermediate of the catalytic reaction, strongly suggests that the Cu+-semiquinone is not an obligatory intermediate of BSAO catalytic pathway.

scholarly journals Structural Basis for the Calmodulin-Mediated Activation of eEF-2K

2022 ◽  
Author(s):  
Andrea Piserchio ◽  
Eta A Isiroho ◽  
Kimberly Long ◽  
Amanda L Bohanon ◽  
Eric A Kumar ◽  
...  
Keyword(s):  
Active Site ◽  
Protein Quality ◽  
Regulatory Element ◽  
Structural Basis ◽  
Calmodulin Binding ◽  
Intimate Association ◽  
Biochemical Studies ◽  
Functional Consequences ◽  
Heterodimeric Complex ◽  
Elongation Phase

Translation is a highly energy consumptive process tightly regulated for optimal protein quality and adaptation to energy and nutrient availability. A key facilitator of this process is the α-kinase eEF-2K that specifically phosphorylates the GTP-dependent translocase eEF-2, thereby reducing its affinity for the ribosome and suppressing the elongation phase of protein synthesis. eEF-2K activation requires calmodulin binding and auto-phosphorylation at the primary stimulatory site, T348. Biochemical studies have predicted that calmodulin activates eEF-2K through a unique allosteric process mechanistically distinct from other calmodulin-dependent kinases. Here we resolve the atomic details of this mechanism through a 2.3 Å crystal structure of the heterodimeric complex of calmodulin with the functional core of eEF-2K (eEF-2KTR). This structure, which represents the activated T348-phosphorylated state of eEF-2KTR, highlights how through an intimate association with the calmodulin C-lobe, the kinase creates a spine that extends from its N-terminal calmodulin-targeting motif through a conserved regulatory element to its active site. Modification of key spine residues has deleterious functional consequences.

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