Friday August 8, 2014
“Structure of mitochondrial ribosome resolved entirely by cryo-EM”
Alexey Amunts, MRC Laboratory of Molecular Biology
During 2 billion years of separate evolution, mitochondrial ribosomes (mitoribosomes) have evolved unique features by acquisition of ~50% more proteins and alteration of their RNA composition.
We resolved a 3.2 Å resolution structure of yeast mitoribosomal large subunit by cryo-EM. The quality of the density maps enabled de novomodel building by following amino acid side chains and nucleic acid bases. The resulting structure reveals 40 proteins, 14 of which are mitochondria unique, and distinctive expansion segments of mitoribosomal RNA.
Methodologically, this work shows that recent advances in cryo-EM can be used to determine structures of comparable quality to X-ray crystallography, without a priorI biochemical knowledge and using much smaller amounts and more heterogeneous starting material. The biological implications of the mitoribosome will be discussed.