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Self-splicing RNA
The Simplest Ribozyme
The hammerhead ribozyme (so named because diagrams of its nucleotide sequence look like a hammer) is the smallest natural ribozyme discovered so far. The example shown here is from PDB entry 1mme. It performs a very simple reaction: the hydroxyl group colored red attacks the neighboring phosphate shown in orange and pink, breaking the RNA chain. The unusual surrounding loop structure holds this linkage in just the right position to promote the break. These types of "nucleolytic" ribozymes are used to solve a special problem encountered by organisms that have circular DNA. When RNA polymerase makes RNA from a DNA circle, it keeps going around and around, making copy after copy strung together in a long continuous strand. Ribozyme self-cleavage sites built into the RNA then break the long strand into smaller functional pieces.Next: Exploring the Structure
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Last changed by: A.Honegger,