Structure of the ribosome from highly developed organisms. Mini review.

Ribosomes of highly evolved organisms are larger than their bacterial counterparts not only in terms of the number of proteins but also in terms of RNA length extensions. Some extensions do not fold into the three-dimensional structure of the ribosome in cryo-EM analysis and cannot be crystallized for X-ray examination. These expansion segments are not visible due to flexibility. In this mini-review, we propose an approach to study the chick embryo ribosome as an example of a highly evolved organism to visualize the expansion segments and study the mechanism of in situ tetramerization and crystallization of ribosomes.