TY - JOUR T1 - Variable stoichiometry among core ribosomal proteins JF - bioRxiv DO - 10.1101/005553 SP - 005553 AU - Nikolai Slavov AU - Stefan Semrau AU - Edoardo Airoldi AU - Bogdan A. Budnik AU - Alexander van Oudenaarden Y1 - 2015/01/01 UR - http://biorxiv.org/content/early/2015/01/28/005553.abstract N2 - Understanding the regulation and structure of the eukaryotic ribosome is essential to understanding protein synthesis and its deregulation in disease. hile ribosomes are believed to have a fixed stoichiometry among their core ribosomal proteins (RPs), some experiments suggest a more variable composition. Reconciling these views requires direct and precise quantification of RPs. We used mass-spectrometry to directly quantify RPs across monosomes and polysomes of budding yeast and mouse embryonic stem cells (ESC). Our data show that the stoichiometry among core RPs in wild-type yeast cells and ESC depends both on the growth conditions and on the number of ribosomes bound per mRNA. Furthermore, we find that the fitness of cells with a deleted RP-gene is inversely proportional to the enrichment of the corresponding RP in polysomes. Together, our findings support the existence of ribosomes with distinct protein composition and physiological function. ER -