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J Derancourt

Publications and source records attributed to J Derancourt.

70 records · Page 4Linked to original sources
PubMed1985

Molecular movements promoted by metal nucleotides in the heavy-chain regions of myosin heads from skeletal muscle.

Molecular movements generated in the heavy-chain regions (27-50-20(X 10(3)) Mr) of myosin S1 on interaction with nucleotides ATP, AMPPNP, ADP and PPi were investigated by limited proteolysis of several enzyme-metal nucleotide complexes in the absence and presence of reversibly bound and crosslinked F-actin. The rate and extent of the nucleotide-promoted conversion of the NH2-terminal 27 X 10(3) Mr and 50 X 10(3) Mr segments into products of 22 X 10(3) Mr and 45 X 10(3) Mr, respectively, were estimated to determine the amplitude of the molecular movements. The 22 X 10(3) Mr peptide was identified by amino acid sequence studies as being derived from cleavage of the peptide bond between Arg and Ile (at position 23 to 24). The 45 X 10(3) Mr peptide, previously shown to represent the NH2-terminal part of the 50 X 10(3) Mr region, would be connected to the adjacent C-terminal 20 X 10(3) Mr region by a pre-existing loop segment of about 5 X 10(3) Mr; the proteolytic sensitivity of the latter region is increased particularly by nucleotide binding. The tryptic reaction proved to be a sensitive indicator of the conformational state of the liganded heavy chain as the rate of peptide bond cleavage in the two regions is dependent on the nature of the bound ligand; it decreases in the order: ATP greater than AMPPNP greater than ADP greater than PPi. It depends also on the nature of the metal present, Mg2+ and Ca2+ being much more effective than K+. Binding of F-actin to the S1-MgAMPPNP complex affords significant protection against breakdown of 27 X 10(3) Mr and 50 X 10(3) Mr peptides, but with concomitant hydrolysis of the 50 X 10(3) Mr-20 X 10(3) Mr junction. Additionally, interaction of MgATP with HMM modulates the tryptic fission of the S1-S2 region. The overall data provide a molecular support for the two-state model of the myosin head and emphasize the involvement of the 50 X 10(3) Mr unit in the mechanism of coupling between the actin and nucleotide binding sites.

Actins↗
PubMed1983

Selective cleavage of the connector segments within the myosin-S1 heavy chain by staphylococcal protease.

The existence of the two connector segments linking the tryptic 50 kDa fragment of skeletal S1 heavy chain to the adjacent 27 kDa and 20 kDa peptides was ascertained by digestion of S1 with staphylococcal protease which was found to act specifically at these particular regions. Three new peptides of Mr 28000, 48000 and 22000 were produced and the novel S1 derivative formed had an intact actin-activated ATPase activity. Amino acid sequence analyses indicated that the 48 kDa and 22 kDa peptides overlap the two connector elements.

Amino Acid Sequence↗
PubMed1983

Determination of cardiac and plasma drug levels during long-term amiodarone therapy.

A study of plasma and cardiac concentrations of amiodarone during the course of long-term oral therapy was made possible by the improvement of analytical high performance liquid chromatography of plasma and tissue extracts. The plasma level was found to increase linearly with the daily dose of the drug, above a threshold value of c. 1 . 9 mg kg-1 day-1. Similarly, the cardiac content increased linearly with the daily dose, with no threshold, showing that the drug is taken up and accumulated in the cardiac tissue, with no obvious difference between atrial and ventricular samples (P greater than 0 . 05). Both plasma and heart showed no saturation at high drug intake, a justification for increasing the oral intake in severe cases. The linear relationship between tissue and blood concentrations allows a prediction of the cardiac level from a simple and routine blood analysis.

Administration, Oral↗
PubMed1978

Binding of calcium by parvalbumin fragments.

Parvalbumin fragments from carp pI 4.47 parvalbumin corresponding to its residues 1--75 and 76--108 bind Ca2+ with affinities corresponding to Kd 0.9 . 10(-4) M and Kd 3 . 10(-3) M, respectively.

Animals↗
PubMed1976

[Tryptic hydrolysis extended to the level of aspartyl bonds].

A quantitative modification of free carboxyl groups in peptides and proteins can be obtained, under mild conditions, by reacting them with ethylenediamine in the presence of N-ethyl-N'-(3-dimethylaminopropyl)-Carbodimide. Aminoethylasparagine and aminoethylglutamine side chains are thus generated in place of the corresponding carboxylic ones. The first kind of residue because of its structure closer to that of lysine, is a point of greater potential trypsic cleavage than the second one. The specificity and yields of this enzymatic cleavage reaction and its possible application in sequence studies are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Disulfide bond as peptide-resin linkage in Boc-Bzl SPPS, for potential biochemical applications.

Use of disulfide bonds for labile linkage in solid-phase peptide synthesis was investigated using polyacrylic polymers (Expansin). Three bifunctional disulfide handles were synthesized for the introduction of disulfide linkage to the synthesis support. This work showed that only N-Boc aminoethyl 2-propionic acid and N-Boc aminoethyl 2-isobutyric acid were fully compatible with Boc/Bzl peptide synthesis and trifluoromethane sulfonic acid side-chain protection. Qualitative and quantitative synthesis results were comparable to those obtained by conventional peptide synthesis using polyacrylic resins. The resulting peptidyl-resins, which swelled in water or aqueous buffers, may be suitable for various biochemical applications, including use as peptide-resin conjugates for antibody production. Thiolysis by aqueous dithiothreitol released mercapto amide peptides suitable for various uses in solution (e.g., direct coupling with activated protein carrier, specific labeling in the mercapto amide group). Partial thiolysis of the disulfide linkage allowed easy post-synthetic adjustment of the peptide loading of peptidyl-resins.

Amino Acid Sequence↗
PubMedDate not supplied

Metabolism of cyclosporin A. IV. Purification and identification of the rifampicin-inducible human liver cytochrome P-450 (cyclosporin A oxidase) as a product of P450IIIA gene subfamily.

A cytochrome P-450 involved in the metabolism of cyclosporin A (CsA) was isolated and purified to electrophoretic homogeneity from human liver microsomes of renal transplant donors. This cytochrome, designated P-450(CsA), exhibited a type I binding spectrum in the presence of CsA with a Ks(app) of 25 microM, a molecular weight of 52 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and a maximal absorbance at 449 nm when reduced in the presence of carbon monoxide. The N-terminal sequence of P-450(CsA), determined by Edman degradation reaction, was 63% homologous with that of the rabbit liver CsA oxidase P-450 3c and 100% homologous with that of the human liver isozyme P-450(HLp/NF), recently identified as the human nifedipine (NF) oxidase. Polyclonal and monoclonal antibodies directed against P-450 3c and P-450(HLp/NF), respectively, recognized native microsomal and highly purified P450(CsA). As observed in the rabbit, human liver microsomes were shown to generate mono- and dihydroxy, as well as dihydroxy and/or monohydroxy N-demethylated, derivatives of CsA. Production of these metabolites was shown to be specifically inhibited by anti-P-450 3c polyclonal antibodies. CsA oxidase, NF oxidase, and erythromycin demethylase were shown to be closely correlated with the level of P-450(CsA) determined from Western blot or enzyme-linked immunosorbent assay. Moreover, these monoxygenase activities and the hepatic level of P-450(CsA) were simultaneously increased in the liver of patients treated for 4 days with 600 mg of rifampicin per day. Finally, NF was shown to be a competitive inhibitor of CsA oxidation and vice versa. We conclude that P-450(CsA) is responsible for most (80%) of CsA oxidase activity in human liver, is encoded by gene P450IIIA3, as is NF oxidase, or a very closely related gene, and is strongly inducible by rifampicin pretreatment.

Blotting, Western↗