process In one study, the net charges (at pH 7.4) of the ribosomal proteins comprising the highly conserved S10-spc cluster were found to have an inverse relationship with the halophilicity/halotolerance levels in bacteria and archaea. In non-halophilic bacteria, the S10-spc proteins are generally basic, contrasting with the overall acidic whole proteomes of the extremely halophiles. The universal uL2 lying in the oldest part of the ribosome, is always positively charged irrespective of the strain/organism it belongs to. In eukaryotes Ribosomes in eukaryotes contain 79–80 proteins and four ribosomal RNA (rRNA) molecules. General or specialized chaperones solubilize the ribosomal proteins and facilitate their import into the nucleus. Assembly of the eukaryotic ribosome appears to be driven by the ribosomal proteins in vivo when assembly is also aided by chaperones. Most ribosomal proteins assemble with rRNA co-transcriptionally, becoming associated more stably as assembly proceeds, and the active sites of both subunits are constructed last. Table of ribosomal proteins In the past, different nomenclatures were used for the same ribosomal protein in different organisms. Not only were the names not consistent across domains; the names also differed between organisms within a domain, such as humans and S. cervisiae, both eukaryotes. This was due to researchers assigning names before the sequences were known, causing trouble for later research. The following tables use the unified nomenclature by Ban et al., 2014. The same nomenclature is used by UniProt's "family" curation. In general, cellular ribosomal proteins are to be called simply using the cross domain name, e.g. "uL14" for what is currently called L23 in humans. A suffix is used for the organellar versions, so that "uL14m" refers to the human mitochondrial uL14 (MRPL14). Organelle-specific proteins use their own cross-domain prefixes, for example "mS33" for MRPS33 and "cL37" for PSRP5. (See the two proceeding citations, also partially by Ban N, for the organelle nomenclatures.) See also Alpha operon ribosome binding site Ribosomal protein L20 leader Mitochondrial ribosome, for a list of its protein subunits References Further reading External links 30S Ribosomal proteins at biochem.umd.edu Ribosomal protein nomenclature visualization from Ban et al., with annotated structures of cellular and organellar ribosomes