[Genetic control of metabolism of mutagenic purine base analogs 6-hydroxylaminopurine and 2-amino-6-hydroxylaminopurine in yeast Saccharomyces cerevisiae].

We studied the effect of inactivation of genes, which control biosynthesis of inosine monophosphate (IMP) and purine salvage and interconversion pathways, on sensitivity of yeast Saccharomyces cerevisiae to the mutagenic and toxic action of 6-hydroxylaminopurine (HAP) and 2-amino-6-hydroxylaminopurine(AHA). It was shown that the manifestation of HAP and AHA mutagenic properties depends on the action of enzyme adenine phosphoribosyltransferase encoded in yeast by APT1 gene. A blockade of any step of IMP biosynthesis, with the exception of the block mediated by inactivation of genes ADE16 and ADE17 leading to the accumulation of 5-aminoimidazole-4carboxamide ribonucleotide (AICAR), was shown to enhanceyeast cell sensitivity to the HAP mutagenic effect; however, it does not affect the sensitivity to AHA.

[Genetic control of metabolism of a mutagenic analog of 6-N-hydroxylaminopurine bases in Saccharomyces cerevisiae yeasts].

Yeasts were shown to utilize 6-substituted adenine analogues as a purine source via the reutilization pathway leading to the formation of inosine monophosphate (IMP). This occurs because the ade12 strains with blocked conversion of IMP into adenosine monophosphate (AMP) cannot grow on media containing the above analogues as a sole purine source. Haploid strains with the double mutation ham1 ade2 or ham1 ade5 were also incapable of growing on a medium with 6-N-hydroxylaminopurine (HAP) as a sole purine source.

[Structural changes in erythrocyte membranes during cooling studied by a spin probe method].

Peculiarities of structural changes in erythrocyte membranes during freezing (from -20 degrees to -50 degrees) were studied by electron paramagnetic resonance method using spin-labelled derivative of stearic acid-5-doxylstearate. It was established that membranes underwent a number of structural reconstructions due to the temperature decrease and water freezing-out. Differences were found in temperature dependences that characterize lipid ordering during probe insertion into membranes of native erythrocytes, white ghosts, and liposomes from total lipids of erythrocyte membranes.