BIOLOGICAL SIGNIFICANCE OF THE SIDE-CHAIN LENGTH OF UBIQUINONE IN SACCHAROMYCES-CEREVISIAE

Ubiquinone (UQ), an important component of the electron transfer syste m, is constituted of a quinone structure and a side chain isoprenoid, The side chain length of UQ differs between microorganisms, and this d ifference has been used for taxonomic study, In this study, we hare ad dressed the importance of the length of the side chain of UQ for cells , and examined the effect of chain length by producing UQs with isopre noid chain lengths between 5 and 10 in Saccharomyces cerevisiae. To ma ke the different UQ species, different types of prenyl diphosphate syn thases were expressed in a S. cerevisiae COQ1 mutant defective for hex aprenyl diphosphate synthesis, As a result, we found that the original species of UQ (in this case UQ-6) had maximum functionality. However, we found that other species of UQ could replace UQ-6, Thus a broad sp ectrum of different UQ species are biologically functional in yeast ce lls, although cells seem to display a preference for their own particu lar type of UQ. (C) 1998 Federation of European Biochemical Societies.