PT  - JOURNAL ARTICLE
AU  - Nikolai Slavov
AU  - Stefan Semrau
AU  - Edoardo Airoldi
AU  - Bogdan A. Budnik
AU  - Alexander van Oudenaarden
TI  - Variable stoichiometry among core ribosomal proteins
AID  - 10.1101/005553
DP  - 2014 Jan 01
TA  - bioRxiv
PG  - 005553
4099  - http://biorxiv.org/content/early/2014/05/26/005553.short
4100  - http://biorxiv.org/content/early/2014/05/26/005553.full
AB  - Understanding the regulation and structure of the eukaryotic ribosome is essential to understanding protein synthesis and its deregulation in disease. Traditionally ribosomes are believed to have a fixed stoichiometry among their core ribosomal proteins (RPs), but recent experiments suggest a more variable composition1–6. 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 ribosomes bound to multiple mRNAs. Together, these findings support the existence of ribosomes with distinct protein composition and physiological function.