70s ribosome translocation intermediate fa-3.6a containing e factor efg/fusidic acid/gdp, mRNA, and tRNA bound in the pe this entry contains the 30s ribosomal subunit a. The 50s su can be found in 4kd9. Molecule b in the same asymmetric uni deposited as 4kda (30s) and 4kdb (50s).
30s ribosomal protein s2. Chain: b. 30s ribosomal protein s3. Chain: c. 30s ribosomal protein s4. Chain: d. 30s ribosomal protein s5. Chain: e. 30s ribosomal protein s6.
Crystal structures of EF-G-ribosome complexes trapped in intermediate states of translocation.
Translocation of messenger and transfer RNA (mRNA and tRNA) through the ribosome
is a crucial step in protein synthesis, whose mechanism is not yet understood.
The crystal structures of three Thermus ribosome-tRNA-mRNA-EF-G complexes
trapped with β,γ-imidoguanosine 5'-triphosphate (GDPNP) or fusidic acid reveal
conformational changes occurring during intermediate states of translocation,
including large-scale rotation of the 30S subunit head and body. In all
complexes, the tRNA acceptor ends occupy the 50S subunit E site, while their
anticodon stem loops move with the head of the 30S subunit to positions between
the P and E sites, forming chimeric intermediate states. Two universally
conserved bases of 16S ribosomal RNA that intercalate between bases of the mRNA
may act as "pawls" of a translocational ratchet. These findings
provide new insights into the molecular mechanism of ribosomal translocation.