Mba1 cofractionates with mitochondrial ribosomes on sucrose gradients. Mba1 cofractionates with mitochondrial ribosomes on sucrose gradients. (A) Wild‐type mitochondria (1 mg) were lysed in Triton buffer and the extract was subfractionated by velocity centrifugation on a continuous sucrose gradient. After fractionation of the gradient, the protein concentration in each fraction was determined. The distribution of the following proteins in the fractions was assessed by Western blotting: F1β, the β‐subunit of the ATPase; Mrps51 and Mrpl20, proteins of the small and large subunit of the mitochondrial ribosome, respectively; Mba1 and Oxa1. (B) Like A, with the exception that the mitochondrial extract was treated with 600 U/ml of bovine pancreatic RNase A for 30 min to disintegrate mitochondrial ribosomes. (C) Mitochondrial extracts were mock treated or incubated with 100 U/ml of RNase A to remove surface‐exposed ribosomal RNA. Remaining ribosomal particles (P) were separated from the supernatant (S) by centrifugation through a high sucrose cushion. Unfractionated samples (T, total) are shown for control. Martin Ott et al. EMBO J. 2006;25:1603-1610 © as stated in the article, figure or figure legend