The Structure of the Ribosome

(Prokaryotic ribosomes)

Proposed secondary structure of 16S rRNA

Many regions are self-complementary and capable of forming double helical segments
Secondary structure is more highly conserved than primary sequence, i.e. complementary mutations evolve to maintain base paring.

3-Dimensional structure of the 70S ribosome

The large subunit has a tunnel about 10 nm long and 2.5 nm in diameter. This tunnel is thought to be the channel that newly assembled polypeptide chains pass through on their way out of the ribosome.

The two subunits interact very tightly and form the active site

Different views: in yellow the 30S (small) subunit; in blue the 50S (large) subunit.

Landmarks of the 30S subunit: h, head; p, platform; ch, channel presumed to be the conduit for mRNA; sp, spur.
Landmarks of the 50S subunit: CP, central protuberance; St, L7/L12 stalk; L1, L1 protein; IC, interface canyon; T, tunnel presumed to be the conduit for the nascent polypeptide chain; T1 and T2, lower tunnel segments, leading to alternative exit sites E1 and E2, respectively.

Next: The X-ray Structure

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