Extended Data Figure 8: The architecture of the mammalian and yeast mitoribosomal central protuberances.

a, The purine–pyrimidine pattern observed in the additional RNA density at the CP as built model (top) and sequence (bottom). Y, pyrimidines; R, purines; N, undetermined. b, The model of CP tRNA with bases in the segment corresponding to the pattern in a coloured accordingly. c, Simplified secondary structure diagram of mitochondrial tRNA^Phe with the segment corresponding to the pattern in a coloured accordingly. d, View of the CP tRNA and the cryo-EM density in the vicinity. Phosphate positions are clearly visible, but the stacked bases merge into continuous strands due to lower local resolution. e, Purines and pyrimidines can be distinguished by their shape. f, Superposition of the large subunit rRNAs of bacterial¹⁵ (23S rRNA in grey, 5S rRNA in yellow), mammalian mitochondrial (16S rRNA in orange; CP tRNA in light green) and yeast mitochondrial ribosomes⁵ (only 84-ES1 shown for clarity, cyan). g, h, Side and top views of the mammalian mitoribosomal CP with the CP tRNA in light green, mL38 in purple, uL18m in blue, mL40 in yellow, mL46 in dark green, mL48 in red and bL31m in orange. i, j, Side and top views of the yeast mitoribosomal CP⁵ with mL38 in purple, mL40 in yellow, mL46 in dark green, bL31m in orange, uL5m in dark red and 84-ES1 in cyan. Homologous proteins in yeast and mammals occupy roughly similar positions, while mammalian mL48 is positioned similarly to yeast uL5m. Mammalian mL38 is shifted slightly towards the solvent side relative to its yeast counterpart. 84-ES1 occupies a similar position as the anticodon stem-loop part of mammalian CP tRNA, and mL40 binds to the RNA minor groove (star) in both cases. k, l, View of the bacterial ribosomal CP¹⁵. 23S rRNA in light grey, 5S rRNA in yellow, uL18 in blue, uL5 in dark red, bL31 in orange, and other ribosomal proteins in light blue.