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Biomedical subjects

J Eder

Publications and source records attributed to J Eder.

At least 37 records · Page 2Linked to original sources
PubMed1993

Refolding of barnase mutants and pro-barnase in the presence and absence of GroEL.

Three mutants of barnase and a pro-barnase variant, which have a variety of different physical properties but the same overall protein structure, were analysed for their folding in the presence of the molecular chaperone GroEL. Mutants were chosen on the basis that changes in their refolding rate constants in solution are not correlated with the changes in their stability. All barnase variants fold considerably more slowly when bound to GroEL. However, barnase refolding on GroEL parallels that in solution: there is a linear relationship between the refolding rate constants, obtained for wild-type and all mutants of barnase, in the presence and absence of GroEL. Barnase is synthesized in vivo with a 13 amino acid pro-sequence attached to the N-terminus. The pro-sequence of pro-barnase is shown by NMR spectroscopy to be devoid of defined structure. The presence of this pro-sequence has no effect on the overall refolding rate constant or the activity of barnase. In the presence of GroEL, the refolding of pro-barnase is retarded relatively more strongly than that of wild-type and the mutant barnase proteins, suggesting that the pro-sequence provides additional binding sites for the chaperone.

Amino Acid Sequence↗
PubMed1992

Protein engineering of a disulfide bond in a beta/alpha-barrel protein.

A disulfide bond has been introduced in the beta/alpha-barrel enzyme N-(5'-phosphoribosyl)anthranilate isomerase from Saccharomyces cerevisiae. The design of this disulfide bond was based on a model structure of this enzyme, built from the high-resolution crystal structure of the N-(5'-phosphoribosyl)anthranilate isomerase domain from Escherichia coli. The disulfide cross-link is spontaneously formed in vitro between residues 27 and 212, located in the structurally adjacent alpha-helices 1 and 8 of the outer helical ring of the beta/alpha-barrel. It creates a loop of 184 residues that account for 83% of the sequence of this enzyme, thus forming a quasi circular protein. The cross-linked mutant enzyme displays wild-type steady-state kinetic parameters. Measurements of the equilibrium constant for the reduction of this disulfide bond by 1,4-dithiothreitol show that its bond strength is comparable to that of other engineered protein disulfide bonds. The oxidized, cross-linked N-(5'-phosphoribosyl)anthranilate isomerase mutant is about 1.0 kcal/mol more stable than the wild-type enzyme, as estimated from its equilibrium unfolding transitions by guanidine hydrochloride.

Aldose-Ketose Isomerases↗
PubMed1992

Stable substructures of eightfold beta alpha-barrel proteins: fragment complementation of phosphoribosylanthranilate isomerase.

The (beta alpha)8 (or "TIM")-barrel protein phosphoribosylanthranilate isomerase from Saccharomyces cerevisiae was cleaved between the sixth and seventh beta alpha module to test the capacity of the resulting fragments to adopt native format autonomously. The fragments, which were expressed from separate coding sequences, were soluble and monomeric. The amino-terminal fragment p1 was compact, possessed an almost nativelike far-UV but a strongly reduced near-UV CD spectrum, and unfolded cooperativity with guanidinium chloride. In contrast, the carboxyl-terminal fragment p2 was less compact than fragment p1, possessed only a weak far-UV and no detectable near-UV CD spectrum, and unfolded noncooperatively. The fragments assembled stoichiometrically to a complex with Kd = 0.2 microM, which was enzymically almost fully active. The rate of assembly was limited by a first-order process, probably the isomerization of the carboxyl-terminal fragment p2 to an assembly-competent structure. These results support a folding mechanism that comprises an intermediate with the first six beta alpha units folded in roughly native format and the last two beta alpha units partially unfolded. The similar behavior of the analogous fragments of the alpha subunit of tryptophan synthease supports the hypothesis that these two (beta alpha)8-barrel proteins have evolved from a common ancestor.

Aldose-Ketose Isomerases↗
PubMed1992

Biosemiotics--a paradigm of biology. Biological signalling on the verge of deterministic chaos.

Biosemiotics is presented as an interdisciplinary approach to the diversity and irregularity of living systems. Emphasizing the interconnectedness by a multitude of signals as a hallmark of life, it goes beyond the scope of a new discipline. As an overarching concept and a new perspective it should be able to integrate a vast array of biological phenomena which till now appear unrelated or incompatible. The basic tenet is that biology, on all levels from molecular biology to ecosystems, can be viewed and investigated as communication, and that life processes can be defined as sign-mediated interaction. Biology thus is, in itself and in all its aspects, natural semiotics with a pronounced proximity to deterministic chaos. Pervading all of biology, the signal is a viable key and a practically feasible access to the understanding of life.

Animals↗
PubMed1985

Elimination of the allatotropic activity in locusts by microsurgical and immunological methods: evidence for humoral control of the corpora allata, hemolymph proteins, and ovary development.

Transection of the nervous connections (NCC I) between the brain and the corpus cardiacum (group 1) and injection of anti-brain antibodies inhibited vitellogenin synthesis and ovary development in virgin Locusta migratoria females. Removal of the neurosecretory material by these methods changed the titer and the electrophoretic pattern of hemolymph proteins, including vitellogenin. Transection of NCC I at some distance from the brain resulted in bulbs with 30-200 micron diameter which were filled with stainable neurosecretory material (group 2). Oocyte maturation was delayed in group 2 but normal eggs were laid. The same happened if group 1 animals received daily injections of JH-III. It is concluded that a humoral factor is involved in the activation of JH-III biosynthesis. The factor is transported through the NCC I and is released into the hemolymph as allatotropin.

Animals↗
PubMed1984

[Cancer mortality in smaller regions with different structures and conditions of air quality].

The study attempts a comparative evaluation of 5 Styrian regions as to their mortality rate of cancer in general as well as cancer of the respiratory system in particular. Regions were not established according to political or administrative districts; instead, communities from areas with homogeneous characteristics as to topography, climate, and air-quality were combined in regions. Among these 5 regions, 2 are industrial centers (region Voitsberg-Köflach with 31.000 inh. and Aichfeld-Murboden with 45.000 inh.), 2 have low to average air pollution (Ausseerland with 13.000 inh. and Deutschlandsberg with 13.000 inh.), 1 is a city with appr. 247.000 inh. (Graz). The disadvantage of the small number of samples was compensated for by observing each region over a period of 11 years. The results clearly demonstrate that the region Voitsberg-Köflach has a statistically significant high mortality rate both of cancer in general as well as of cancer of respiratory system in particular. The collected data provide ample ground for the assumption that environmental conditions are to a large degree responsible for the high mortality rate; this study will provide the basis for systematic investigations of its causes.

Adolescent↗
PubMed1977

Immunoassay for honey bee cytochrome c in single animals with cytochrome c-coated bacteriophages: a sensitive tool for the study of caste formation in the honey bee, Apis mellifera.

The development of a sensitive viroimmunoassay for honey bee cytochrome c and its usage for early detection of caste differentiation is described. Pure honey bee cytochrome c was isolated from workers and used to produce antibodies in rabbits. Bacteriophage T4 was chemically modified by covalent attachment of honey bee cytochrome c using tolylene-2,4-diisocyanate as a cross-linking agent. The immunospecific inactivation of this bacteriophage-cytochrome c conjugate by anti-cytochrome c antibodies can be inhibited by free cytochrome c. In quantitative determinations, 50% inhibition is reproducibly achieved at a concentration of 6 ng/ml (5 pmol/ml) and as little as 0.3 ng/ml (0.25 pmol/ml) could be detected by this system. Cytochrome c concentrations were measured in individual animals and substantial differences corresponding larval stages of worker and queen bees are reported.

Antibodies↗
PubMed1977

[Investigations of some chemical compounds produced by the incineration of old tires in the open air (author's transl)].

The chemical compounds which are discharged from the site at which old tires are incinerated in the open air roughly corresponded to those of waste water. In the smoke "mushroom" above the site of incineration, at a height of 31 to 40 metres, many types and large quantities of polycyclic aromatic and also cancerogenic hydrocarbons were found adsorbed on soot particles.

Adsorption↗
PubMed1969

[Initial clinical experiences with the administration of new amino acid derivatives in the treatment of malignant tumors].

A report is given on the first clinical experience made with the application of new amino acid compounds in the therapy of malignant tumors. The established good compatibility of the substances allows long-termed treatments with great variability of individual dosage. The regressions of tumors observed and the frequent improvement of the general status, even in advanced stages of tumors, should give rise to a broad investigation of the available tumor inhibitors.

Adolescent↗