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Biomedical subjects

M Tessier

Publications and source records attributed to M Tessier.

9 recordsLinked to original sources
PubMed1997

Isolation and characterization of the carotenoid biosynthesis genes of Flavobacterium sp. strain R1534.

The Gram-negative bacterium Flavobacterium sp. strain R1534 is a natural producer of zeaxanthin. A 14 kb genomic DNA fragment of this organism has been cloned and a 5.1 kb piece containing the carotenoid biosynthesis genes sequenced. The carotenoid biosynthesis cluster consists of five genes arranged in at least two operons. The five genes are necessary and sufficient for the synthesis of zeaxanthin. The encoded proteins have significant homology to the crtE, crtB, crtY, crtI and crtZ gene products of other carotenogenic organisms. Biochemical assignment of the individual gene products was done by HPLC analysis of the carotenoid accumulation in Escherichia coli host strains transformed with plasmids carrying deletions of the Flavobacterium sp. strain R1534 carotenoid biosynthesis cluster.

Alkyl and Aryl Transferases↗
PubMed1988

The limited photochemical activity of solid aggregated forms of bovine rhodopsin.

The visual pigment rhodopsin has been purified and depleted of detergent. Under these conditions, the pigment strongly aggregates. When dried, a significant fraction of these aggregates appear insensitive to light. We have characterized them by means of absorption and photoacoustic spectroscopies and we find that their photochemical behavior is best explained by a limited activity that does not reach photointermediates beyond the lumirhodopsin step in the bleaching sequence of rhodopsin. We interpret this result as an indication of a significant conformational change of the protein during the transition from lumi- to meta-rhodopsin.

Animals↗
PubMed1983

Are interactions with phospholipids responsible for pharmacological activities of cardiotoxins?

Cardiotoxins are small basic proteins (7 000 daltons) that are found in the venoms of Elapidae snakes. Although they are structurally close to alpha-neurotoxins present in the same secretions, their activity is related to their ability to interact with every cell membrane inducing, near micromolar concentration, the modification of its biological properties and/or physical structure. The mode of action of cardiotoxins, on a molecular level, is still under investigation. However, lipid-protein interactions are more and more involved in their binding to membrane and in their activities. Using new experimental data a better definition of phospholipid-cardiotoxin interaction is arrived at and a tentative molecular explanation of the pharmacological activities of these proteins is presented and discussed.

Amino Acid Sequence↗
PubMed1983

Amino-acids condensations in the preparation of N alpha-9-fluorenylmethyloxycarbonylamino-acids with 9-fluorenylmethylchloroformate.

Synthesis of N alpha-9-fluorenylmethyloxycarbonyl (Fmoc) amino-acids by reaction of free amino-acids (glycine and alanine) with 9-fluorenylmethylchloroformate leads to formation of small amounts of Fmoc-dipeptide which are difficult to eliminate by crystallization. The alternative way to prepare Fmoc-amino-acids by reacting the Fmoc-chloride first with sodium azide and then with the free amino-acid eliminates this side reaction, at least for glycine and alanine.

Amino Acids↗
PubMed1982

Structure-function relationships for cardiotoxins interacting with phospholipids.

Four cardiotoxins (CTX I-IV) from Naja mossambica mossambica were compared for their ability to interact with phospholipid vesicles and their capacity to bind erythrocytes. It is concluded that the affinity of the toxins always increases in the order: I approximately equal to II less than III less than IV. The binding is specific for charged lipids even in lipid mixtures. Proteolytic attack of the free and lipid-bound cardiotoxin indicates that at least the first loop Leu1-Thr13 is at the lipid contact. Tryptic and synthetic peptides constitutive of this loop are shown to interact with lipids. Arg5 residue increases the affinity toward the bilayer. The Raman spectra of lipid-bound cardiotoxin indicate a secondary and tertiary structure mainly similar to that of the free toxin. On charged lipids cardiotoxins induce a decrease of the enthalpy and an increase of disorder without change in the transition temperature; at saturating amounts of toxin the transition is abolished. In binary mixtures of phosphatidylcholine and charged lipids the observed effects can be accounted by a phase separation induced by the toxin.

Amino Acid Sequence↗