Pyrrolysine

At the turn of the 1970s and 1980s, the twenty-first - selenocysteine ​​(Sec) - and recently the twenty-second, pyrrolysine (Pyl) were added to the classically coded twenty amino acids . Unlike all previous amino acids, triplets are encoded, which normally serve as signals to terminate translation (see genetic code ). Specifically, the triplet UGA serves for the incorporation of selenocysteine ​​and UAG for the incorporation of pyrrolysine.

The occurrence of pyrrolysine (Pyl) is so far limited to members of the Methanosarcinaceae family of archaebacteria and the bacterium Desulfitobacterium hafniense . The involvement of pyrrolysine in the metabolism of these organisms is related to their exceptional ability to use methylamines as an energy source. They do this through the enzymes methylaminomethyltransferases , and for their successful synthesis it is necessary that one UAG triplet located in the reading frame of their mRNA is read not as a termination signal , but as a signal for pyrrolysine incorporation. In addition, D. hafniense encodes a system that incorporates selenocysteine ​​into proteins , so this bacterium is the only known organism that uses all 22 amino acids in photosynthesis.

Related Articles

• Selenocystein
• Amino acids

Source

At the request of the author and with the permission of the publisher, adapted from Jonák J: RNA in proteosynthesis. Coding for selenocysteine ​​and pyrrolysine. Živa 5/2007, 195-198.

• JONÁK, J. RNA in proteosynthesis. Genetic code and preparation of aminoacyl–tRNA. Alive [online]. 2007, year 2007, vol. 5/2007, pp. 195-198, also available from <http://ziva.avcr.cz/files/ziva/pdf/rna-v-proteosynteze-geneticky-kod-a-priprava-amino.+pdf >. ISSN 0044-4812.