|MadSci Network: Molecular Biology|
Dear Becky, your question is quite interesting because recently the scientific community seemed to finally have answered a part of that. But before going straight to the point, I think that we need here a little reminder to put a perspective to the whole story. First of all, the ribosome is the apparatus in the cell that produces every proteins. Proteins are used in a variety of way (cell walls, production of energy, etc). In order to know which protein to make, the ribosome must read a messenger RNA. This RNA encodes a unique sequence that is specific for a certain protein (sometimes one messenger can gives several protein by a process known as splicing). For the records, the messenger is produced in the nucleus and the sequence is encoded in the so-called genome. So, coming back to the ribosome, it is obvious that it is an essential part in the life cycle of any cell. The ribosomes are themselves made of proteins and RNA (ribosomal RNA or rRNA). Now, let's talk about your question at this point. When people started working on the ribosome, it was believed that the proteins were doing the actual job of making the proteins from the messenger. The rRNA was believed to be only involved in the reading of the messenger. However, when significant part of the proteins were removed, the activity was still observed. This observation shown that maybe the RNA was the catalyst in the reaction but it was not really believed by many scientist (I presume !). But recently (last year) a high resolution crystal structure of a ribosome's part was obtained by the Steitz lab in Yale. They observed that the catalytic core (where the actual job of making the protein is performed) was entirely composed of RNA. Therefore, it seems that the RNA has the catalytic role in the ribosome which was a surprise for a lot of people ! In fact, this is not new since there are some RNA that are known to have catalytic property (ribozyme). These findings have shed light in the RNA community and now scientists believe that perhaps RNA catalysis is a much more important phenomena than previously believed (perhaps also in splicing). I hope that you understand a bit more about RNA ! Daniel
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