[Comparative structural and functional characteristics of different forms of Saccharomyces cerevisiae red pigment and its synthetic analogue].

Structural and functional characteristics of the yeast red pigment (product of polymerization of N1-(beta-D-ribofuranosyl)-5-aminoimadazole), isolated from adel 1 mutant cells of Saccharomyces cerevisiae, its deribosylated derivatives (obtained by acid hydrolysis) and its synthetic pigment analogue (product of polymerization of N1-methyl-5-aminoimadazole in vitro) has been obtained. Products of in vitro polymerization were identified using mass spectrometry. The ability of these pigments to inhibit amyloid formation using insulin fibrils was compared.

[The effect of red pigment of Saccharomyces cerevisiae on insulin fibril formation in vitro].

The effect of the yeast red pigment, the result of polymerization of AIR, and of its low molecular weight derivative (presumably devoid of phosphoribosyl moiety) on the formation of amyloid fibrils in vitro was studied. Both the red pigment and its derivative, the result of acid hydrolysis of the original pigment, were shown to diminish the intensity of amyloid bound Thioflavine T fluorescence. Correlation between the decrease of the intensity of Thioflavine T fluorescence and the concentration of both forms of the red pigment was demonstrated.

[The effect of red pigment on amyloidization of yeast proteins].

Amyloid bound thioflavine T fluorescence was studied in the lysates of yeast strains carrying mutations in genes ADE1 or ADE2 and accumulating red pigment, a result of polymerization of aminoimidazoleribotide (an intermediate of adenine biosynthesis). The fluorescence is drastically enhanced in the case of cells grown in media containing high concentration of adenine (100 mg/l) that blocks accumulation of red pigment. Blocks at first stages of purine biosynthesis de novo also impede red pigment and lead to the same effect on thioflavine fluorescence.

[Comparison of crude lysate pellets of isogenic strains of yeast with different prion composition: identification of a set of prion-associated proteins].

A new approach: comparative analysis of proteins of the pellets of crude cell lysates of isogenic strains of Saccharomyces cerevisiae differing by their prion composition permitted to identify a large group of prion-associated proteins in yeast cells. 2D-electrophoresis followed by MALDI-analysis of a recipient [psi-] strain and of [PSI+] cytoductant led to identification of 35 proteins whose aggregation state responded to a shift of prion(s) content. Approximately half of these proteins belonged to functional groups of chaperones and enzyme involved in glucose metabolism.

[Estimating of changes in the amyloid and prion content of yeast cells].

An attempt was made at estimating the overall amyloid content of yeast cells by treating crude cellular lysates with thioflavin T, the agent specifically staining amyloid fibrils. We demonstrated that overproduction of the yeast chaperone Hsp104p, as well as GuHCI treatment of the [PSI+] cells led both to elimination of the [PSI+] factor and to a stable decrease of the overall amyloid content estimated by intensity of fluorescence (IF) of the thioflavin T. At the same time, overexpression of gene SUP35, coding the protein prionizable to [PSI+], led to generation of [PSI+] clones with higher IF of thioflavin T.