ABC1, a novel yeast nuclear gene has a dual function in mitochondria: it suppresses a cytochrome b mRNA translation defect and is essential for the electron transfer in the bc 1 complex.

Abstract

We have cloned and sequenced a novel yeast nuclear gene ABC1 which suppresses, in multicopy, the cytochrome b mRNA translation defect due to the nuclear mutation cbs2‐223. Analysis of the ABC1 gene shows that it is weakly expressed, it could code for a protein of 501 amino acids which has a typical presequence of a protein imported into mitochondria and which does not display a strong similarity to any known protein. Inactivation of the ABC1 gene is not lethal to the cell but leads to a respiratory defect: no oxygen uptake and no growth on non‐fermentable media. A total absence of NADH‐cytochrome c oxidoreductase and succinate‐cytochrome c oxidoreductase activities concomitant with the presence of specific dehydrogenases, suggests a block in the bc 1 segment of the respiratory chain. However, all the cytochromes are spectrally detectable. Cytochrome b is quite efficiently reduced while cytochromes c1 and c are not. The function of ABC1 in the suppression of a defect in apocytochrome b mRNA translation and in the activity of the bc1 complex suggests that the ABC1 protein would be a novel chaperonin involved both in biogenesis and bioenergetics of mitochondria.

Novel Families of Putative Protein Kinases in Bacteria and Archaea: Evolution of the “Eukaryotic” Protein Kinase Superfamily

“…One of the ABC1 paralogs in A. thaliana is most closely related to the ABC1 proteins found in the cyanobacterium Synechocystis, suggesting an independent chloroplast origin (we label this protein as chABC1, to distinguish it from the other paralog in A. thaliana). The established role of S. cerevisiae ABC1 (YGL119W) in the function of the mitochondrion (Bousquet et al 1991;Brasseur et al 1997) lends additional support to an ancient bacterial origin for this protein family. The only archaeal ABC1 family member (found in M. thermoautotrophicum) is most closely related to the bacterial ABC1 proteins and may represent a more recent horizontal transfer.…”

“…Mutants in the aarF gene of Providencia stuarti and the yigR gene from E. coli are both deficient in the synthesis of ubiquinone (cofactor Q) (Macinga et al 1998). The prototypic family member, S. cerevisiae ABC1 (YGL119W), is defective in aerobic respiration because of a reduction in the activity of the mitochondrial bc1 complex that can be overcome by exogenously supplied quinones (Bousquet et al 1991;Brasseur et al 1997). One possible explanation for the expansion of this family in the cyanobacterium Synechocystis could be the role of the Q-cycle in capturing energy from photosynthesis.…”

AtOSA1, a Member of the Abc1-Like Family, as a New Factor in Cadmium and Oxidative Stress Response

“…The members of Abc1 protein family have been identified in both pro-and eukaryota, for example, AarF from Escherichia coli (Macinga et al, 1998) and ABC1 from yeast (Bousquet et al, 1991). It is worth emphasizing Figure 2.…”

“…For this purpose, we used the yeast S. cerevisiae deletion mutant W303-1A abc1THIS3 deficient in the endogenous ABC1 activity (Hsieh et al, 2004). Deletion of the ABC1 gene in yeast disturbs the function of the respiratory chain and prevents growth of this mutant strain on media containing nonfermentable carbon sources such as glycerol (Bousquet et al, 1991). The expression of the entire AtOSA1 gene, including its targeting presequence in the W303-1A abc1THIS3 strain, did not restore growth of this mutant on glycerol-containing media.…”

“…The Abc1 protein family originates from the Saccharomyces cerevisiae ABC1 gene, which has been isolated as a suppressor of a cytochrome b mRNA translation defect (Bousquet et al, 1991). The mitochondrial ABC1 in yeast was suggested to have a chaperone-like activity essential for a proper conformation of cytochrome b complex III (Brasseur et al, 1997).…”