Figure 7.

Co-evolution of ribosomes to utilize natural variants of initiator tRNA. Binding of 1^st AU mutant tRNA^fMet in E. coli and S. medicae WSM419 ribosomes. (i) Total ribosomal cell-free extracts of E. coli KL16ΔmetZWVΔmetY sustained on wild-type metY or the 1^st AU metY or from S. medicae were separated on 15–35% sucrose gradient and analyzed by O.D.₂₅₄. (ii) The tRNAs from the individual peaks were analyzed by northern blotting using tRNA^fMet probe (the same probe specific to E. coli was used as it differed only by single nucleotide with S. medicae initiator tRNA). (iii) The fractional distribution of tRNA^fMet across the profile.