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Non-random base composition in codons of mitochondrial cytochrome b gene in vertebrates.

100%

Prusak B., Grzybowski T.

Acta Biochimica Polonica

2004

vol. 51

issue 4

897-905

Cytochrome b is the central catalytic subunit of the quinol:cytochrome c oxidoreductase of complex III of the mitochondrial oxidative phosphorylation system and is essential to the viability of most eukaryotic cells. Partial cytochrome b gene sequences of 14 species representing mammals, birds, reptiles and amphibians are presented here including some species typical for Poland. For the analysed species a comparative analysis of the natural variation in the gene was performed. This information has been used to discuss some aspects of gene sequence - protein function relationships. Review of relevant literature indicates that similar comparisons have been made only for basic mammalian species. Moreover, there is little information about the Polish-specific species. We observed that there is a strong non-random distribution of nucleotides in the cytochrome b sequence in all tested species with the highest differences at the third codon position. This is also the codon position of the strongest compositional bias. Some tested species, representing distant systematic groups, showed unique base composition differing from the others. The quail, frog, python and elk prefer C over A in the light DNA strand. Species belonging to the artiodactyls stand out from the remaining ones and contain fewer pyrimidines. The observed overall rate of amino acid identity is about 61%. The region covering Qo center as well as histidines 82 and 96 (heme ligands) are totally conserved in all tested species. Additionally, the applied method and the sequences can also be used for diagnostic species identification by veterinary and conservation agencies.

Conserved Cys residue influences catalytic properties of potato endo-(1→3)-β-glucanase GLUB20-2

75%

Witek A. I., Witek K., Hennig J.

Acta Biochimica Polonica

2008

vol. 55

issue 4

791-797

The synthesis and degradation of (1→3)-β-glycosidic bonds between glucose moieties are essential metabolic processes in plant cell architecture and function. We have found that a unique, conserved cysteine residue, positioned outside the catalytic centre of potato endo-(1→3)-β-glucanase - product of the gluB20-2 gene, participates in determining the substrate specificity of the enzyme. The same residue is largely responsible for endo-(1→3)-β-glucanase inhibition by mercury ions. Our results confirm that the spatial adjustment between an enzyme and its substrate is one of the essential factors contributing to the specificity and accuracy of enzymatic reactions.

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2 Acta Biochimica Polonica

1 2008

1 2004

1 Grzybowski T.

1 Hennig J.

1 Prusak B.

1 Witek A. I.

1 Witek K.

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Non-random base composition in codons of mitochondrial cytochrome b gene in vertebrates.

Conserved Cys residue influences catalytic properties of potato endo-(1→3)-β-glucanase GLUB20-2