Figure 1.

The Arabidopsis COX11 homolog shares structural and sequence similarities with yeast COX11, but cannot functionally complement it. (A) The A. thaliana (A. t.) and S. cerevisiae (S. c.) protein sequence were retrieved from the GenBank database and aligned. The vertical lines (I) indicate identical residues between the two sequences, while the colons (:) and periods (.) represent conservative substitutions with strongly and weakly similar properties, respectively. Cysteines are labeled yellow. The putative copper-binding motifs are boxed. The predicted cleavable N-terminal targeting signals are double underlined. The predicted transmembrane domains are shown in bold red letters, while the predicted α-helices and β-sheets are highlighted in green and gray, respectively. (B) Results from a respiratory competence test of yeast Δcox11 stains moderately overexpressing either full-length S. cerevisiae COX11, Arabidopsis COX11, or sequences encoding the chimeric proteins CHYM-1 or -2. Schematic diagrams of the proteins depict their composition (N, N-terminal region; C, C-terminal region; ^*, transmembrane domain) and the origin of the respective regions (S. cerevisiae, blue; A. thaliana, green). Serial dilutions of yeast strains were spotted on fermentable glucose media (YPD) or respiratory media (YPEG, ethanol + glycerol media supplemented with 0.5 mM CuSO₄).