PMID:15734919

Citation	Chang, IF, Szick-Miranda, K, Pan, S and Bailey-Serres, J (2005) Proteomic characterization of evolutionarily conserved and variable proteins of Arabidopsis cytosolic ribosomes. Plant Physiol. 137:848-62
Abstract	Analysis of 80S ribosomes of Arabidopsis (Arabidopsis thaliana) by use of high-speed centrifugation, sucrose gradient fractionation, one- and two-dimensional gel electrophoresis, liquid chromatography purification, and mass spectrometry (matrix-assisted laser desorption/ionization time-of-flight and electrospray ionization) identified 74 ribosomal proteins (r-proteins), of which 73 are orthologs of rat r-proteins and one is the plant-specific r-protein P3. Thirty small (40S) subunit and 44 large (60S) subunit r-proteins were confirmed. In addition, an ortholog of the mammalian receptor for activated protein kinase C, a tryptophan-aspartic acid-domain repeat protein, was found to be associated with the 40S subunit and polysomes. Based on the prediction that each r-protein is present in a single copy, the mass of the Arabidopsis 80S ribosome was estimated as 3.2 MD (1,159 kD 40S; 2,010 kD 60S), with the 4 single-copy rRNAs (18S, 26S, 5.8S, and 5S) contributing 53% of the mass. Despite strong evolutionary conservation in r-protein composition among eukaryotes, Arabidopsis 80S ribosomes are variable in composition due to distinctions in mass or charge of approximately 25% of the r-proteins. This is a consequence of amino acid sequence divergence within r-protein gene families and posttranslational modification of individual r-proteins (e.g. amino-terminal acetylation, phosphorylation). For example, distinct types of r-proteins S15a and P2 accumulate in ribosomes due to evolutionarily divergence of r-protein genes. Ribosome variation is also due to amino acid sequence divergence and differential phosphorylation of the carboxy terminus of r-protein S6. The role of ribosome heterogeneity in differential mRNA translation is discussed.
Links	PubMed PMC1065386 Online version:10.1104/pp.104.053637
Keywords	Amino Acid Sequence; Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins/chemistry; Arabidopsis Proteins/genetics; Arabidopsis Proteins/physiology; Conserved Sequence/genetics; Conserved Sequence/physiology; Evolution, Molecular; Molecular Sequence Data; Multigene Family; Phosphorylation; Phylogeny; Protein Processing, Post-Translational; Ribosomal Proteins/chemistry; Ribosomal Proteins/genetics; Ribosomal Proteins/physiology
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