Prokaryotic release factors

There are three known prokaryotic release factors involved in the termination of translation. RF1 and RF2 are so called class 1 release factors and RF3 a class 2 release factor.

The release factors provide the means of termination by having a conformation that mimics that of tRNA molecules. The decoding release factor binds to the A site of the ribosome and directly recognises the stop codon. Once RF1 (or RF2) is bound to the ribosome, the polypeptide is released, and the ribosome and release factors disassemble, thus completing the process of translation.

...
Wikipedia