Biomedical subjects

L Moroder

Publications and source records attributed to L Moroder.

205 records · Page 12Linked to original sources

PubMedDate not supplied

Idiotypic vaccine for treatment of human B-cell lymphoma. Construction of IgG variable regions from single malignant B cells.

Immunoglobulin idiotypes (Id) of malignant B cells represent highly specific markers which can be used for vaccination. PCR-amplification of immunoglobulin genes enables the rapid production of large amounts of Id vaccines. However, the separate amplification and subsequent recombination of heavy and light chains can lead to a loss of the relevant Id. To preserve the original chain pairs, we used single malignant B cells derived from an immunocytoma patient. Cytoplasm was extracted and the mRNA transcribed into cDNA. The VH and VL genes were then amplified by PCR and cloned into a vector for expression in E. coli. Id production was checked using an anti-Id mouse monoclonal Ab raised against the patient's tumor-specific IgG. One out of 3 constructs expressed the relevant Id. Analysis of the first 31 light chain residues revealed an identical sequence for the malignant B cells' IgG and the recombinant Id construct. Exchange of either the heavy or light chain with an unrelated chain resulted in loss of the Id. An unrelated sequence derived from the c-myc protein is coupled to the Id vaccine. The lymphoma patient was shown to have Abs to the c-myc sequence. This sequence therefore, increases the Id+ Ab's antigenicity. CD spectroscopy showed an alpha-helical structure for the c-myc epitope. In conclusion, a B-cell lymphoma autovaccine was produced containing immunogenic sequences that do not alter the steric conformation of the tumor-specific Id.

Animals↗

PubMedDate not supplied

The substrate translocation channel of the proteasome.

The core particle (CP) of the yeast proteasome is composed of four heptameric rings of subunits arranged in a hollow, barrel-like structure. We have found that the CP is autoinhibited by the N-terminal tails of the outer (alpha) ring subunits. Crystallographic analysis showed that deletion of the tail of the alpha3 subunit opens a channel into the proteolytically active interior chamber of the CP, thus derepressing peptide hydrolysis. In the latent state of the particle, the tails prevent substrate entry by imposing topological closure on the CP. Inhibition by the alpha subunit tails is relieved upon binding of the regulatory particle to the CP to form the proteasome holoenzyme. Opening of the CP channel by assembly of the holoenzyme is regulated by the ATPase domain of Rpt2, one of 17 subunits in the RP. Thus, open-channel mutations in CP subunits suppress the closed-channel phenotype of an rpt2 mutant. These results identify a specific mechanism for allosteric regulation of the CP by the RP.

Adenosine Triphosphatases↗

PubMedDate not supplied

Chalcogen-analogs of amino acids. Their use in X-ray crystallographic and folding studies of peptides and proteins.

Using methionine-auxotrophic Escherichia coli strains quantitative biosynthetic replacement of the methionine residues by seleno- and telluromethionine but not by methoxinine was achieved in various model proteins, clearly indicating a limited tolerance in the editing range of methionyl-tRNA synthetase. For expression of the protein variants the acetyl derivatives of the chalcogen-analogs of methionine, obtained by a new and highly efficient synthetic procedure, proved to be the ideal source in the growth media as they were found to be significantly more stable than the underivatized methionine analogs. The conformational properties in solution, the folding and unfolding parameters as well as X-ray crystallographic data confirmed the highly isomorphous character of the atomic mutants and thus the usefulness of this concept in X-ray analysis of proteins. Quantitative replacement of cysteine residues by selenocysteine has recently been achieved using cysteine-auxotrophic E. coli strains, but a selective replacement of cysteine residues by employing the natural translational machinery of selenocysteine is also conceivable. We have therefore performed a detailed study on synthetic selenocysteine-peptides in order to determine the redox potential of this cysteine analog, and thus the ability of related peptide and protein analogs to undergo the correct oxidative folding. Since the redox potential of selenocysteine was found to be significantly more reducing than that of the parent amino acid, selective formation of a diselenide bridge in presence of additional cysteine residues is highly favored as well documented in the case of the synthetic bis-selenocysteine-endothelin I analog. These results confirm that even cysteine residues may represent an interesting target for the design and expression of isomorphous heteroatomic analogs of proteins.

Amino Acids↗

PubMedDate not supplied

Molecular modelling studies on G protein-coupled receptors: from sequence to structure?

In pharmaceutical research G protein-coupled receptors (GPCR) emerged as a superfamily of prominent drug targets. Extensive protein sequence analyses on GPCRs revealed a common protein topology consisting of a membrane-spanning seven-helix bundle, which is believed to accommodate the binding site for low-molecular weight ligands. Enormous efforts are undertaken to generate GPCR structural models by means of molecular modelling, since these have already been shown to aid the process of lead structure finding and optimisation in that they provide atomistic models for structure-based drug design approaches. One of the most critical steps in modelling the transmembrane domains of GPCRs is the assignment of the putative transmembrane sequence stretches from multiple protein sequence alignment analyses. This study focuses on the comparative evaluation of protein sequence analysis tools, such as periodicity analyses, multiple sequence analyses or directional helix descriptors, especially developed for modelling the 7TM domains of GPCRs. In this context we will demonstrate that from application of different methods contradictory results can be obtained for the identification of the putative transmembrane sequence stretches of peptide-binding GPCRs, as exemplified with a comprehensive protein sequence analysis study based on the most prominent members of that receptor class (angiotensin II, CCK/gastrin, interleukin 8, endothelin, etc.).

Animals↗

PubMedDate not supplied

[Total synthesis of human big gastrin I and the 32-leucine analogue (author's transl)].

Synthetic Peptide Hormones, Human Big Gastrin I. A new total synthesis of the tetratriacontapeptide amide corresponding to the proposed primary structure of human big gastrin I is described. The synthetic route was based on the preparation of six suitably protected fragments, related to sequence 28-34, 23-27, 21-22, 15-20, 9-14, and 1-8, to be used as building blocks for the total synthesis. The protecting groups were selected according to the Schwyzer-Wünsch strategy of maximum side chain protection based on tertiary alcohols, also for the imidazol function of histidine. Subsequent assembly of the six fragments by three different pathways using the highly efficient Wünsch-Weygand condensation procedure to ensure minimum racemization, followed by deprotection of the synthetic products via exposure to trifluoroacetic acid and final purification by ion-exchange chromatography on DEAE-Sephadex A-25 and partition chromatography on Sephadex G-25, led to human big gastrin I, homogeneous within the limits of the analytical methods used. The biological activity of the synthetic product proved to be 50 percent higher than that of human little gastrin I. The 32-leucine analogue of human big gastrin I was prepared in the same way.

Amino Acid Sequence↗

PubMedDate not supplied

N alpha-trifluoroacetylation of N-terminal hydroxyamino acids: a new side reaction in peptide synthesis.

In the synthesis of the double-chain bis-cystinyl hinge fragment 225-232/225'-232' of the human IgG1, which contains two N-terminal threonine residues, the final acidolytic deprotection step, with 99% aqueous trifluoroacetic acid, was accompanied by formation of remarkable amounts of an unknown side product. This has been identified as the N alpha-mono-trifluoroacetylated product; however, even bis-trifluoroacetylation was found to occur by prolonged exposure of the parallel dimer to the reaction medium. Similarly, the model compounds H-Thr(tBu)-Phe-OH, [Boc-Thr(tBu)-Cys-OH]2 and Boc-Thr(tBu)-Cys(StBu)-Ala-OH were acylated by treatment with trifluoroacetic acid at rates that suggest a rather pronounced sequence dependency. Since, on the other hand, the model compound [Boc-Ala-Cys-OH]2 was not trifluoroacetylated at all under identical conditions, the reaction has to proceed prevalently via intermediate formation of the trifluoroacetyl ester of N-terminal hydroxyamino acids, followed by O-->N shift according to the hydroxyoxazolidine mechanism. The experimental data indicate also that under favored conditions aminolysis of the trifluoroacetyl ester via an inter- or intramolecular pathway may contribute to the overall reaction rate.

Acetylation↗

PubMedDate not supplied

Synthesis of neo-glycosylated L-alanyl-D-isoglutamine derivatives as potential immunoadjuvants.

The synthesis is described for muramyl-dipeptide-related amphiphilic analogs, where 1,10-diaminodecane served as a lipophilic C-terminal linker for the preparation of a bidentated L-alanyl-D-isoglutamine derivative and incorporation of aldonic and uronic acids at the N-termini as hydrophilic cores. For the N-acylation steps via lactones, suitable conditions were elaborated to allow for the use of unprotected or minimally protected aldonic and uronic acid lactones, respectively. These procedures may represent a useful general approach for the synthesis of neoglycopeptides.

Acetylmuramyl-Alanyl-Isoglutamine↗