Ribosomes are large molecular machines made up of RNA and a large number of proteins that are responsible for the protein synthesis of all living things on Earth. In eukaryotes, ribosome assembly is a very complex process. Ribosomes need to be temporarily combined with a large number of assembly factors during the maturation process to form a series of ribosome precursor complexes. Small subunit ribosomes form two major intermediates during assembly: early 90S and late pre-40S precursors. The 90S precursor is a giant complex containing, in addition to ribosomal RNA and protein components, about 50 non-ribosomal proteins and U3 snoRNA with molecular weights up to 5 million Daltons. The Ye Kepeng Laboratory of the Institute of Biophysics, Chinese Academy of Sciences obtained three electron density maps of the 90S ribosomal precursor of budding yeast using cryo-electron microscopy and single-particle reconstruction. The overall resolution of the best density map reached 4.5. Ai. The researchers constructed a nearly complete 90S structural model using known crystal structures, de novo modeling, and chemically cross-linked mass spectrometry data. The structure of 90S shows that the nascent ribosomal small subunits fold to form multiple isolated substructures and bind to a large number of assembly factors. The 5' spacer region of the ribosomal precursor RNA, U3 snoRNA, and a large number of assembly factors form a giant pedestal that supports the structure of the nascent ribosome. The structure also reveals novel ways of binding U3 snoRNA to ribosomal precursor RNA. This structure is of great significance for understanding the early assembly principles of ribosomal small subunits and the function of assembly factors. The Molecular architecture of the 90S small subunit pre-ribosome, which covered the work, was published online in eLife magazine on February 28. Squid Rings Raw,Frozen squid rings,This year's Squid Rings ZHOUSHAN GENHO FOOD CO.,LTD , https://www.genho-food.com