Yeast ribosomal proteins

Summary Homology maps between bacteriophages 81, 80 and were constructed on the basis of electron microscope observation of DNA heteroduplexes. In 81/80 heteroduplex, the left half and the right terminal region of 13% the total molecular length were highly homologous, while the remaining region covering the early gene cluster was entirely nonhomologous. In 81/ heteroduplex, high-degree homologies were detected at the left 14% terminal region covering the head gene cluster, the central 3.8% region covering the att-int-xis region and the 1.3% Q homology region. Low-degree homologies of shorter length were scattered at the tail gene cluster, b2 region, cIII region, PQ region and SR region. Comparing our results with the homology maps of other lambdoid phages reported by Simon et al. (1971) and Fiandt et al. (1971), a phylogenic relation of 81 to other lambdoid phages and the role of recombination in the course of divergence of lambdoid phages are discussed.     

Yeast ribosomal proteins: VII. Cytoplasmic ribosomal proteins from Schizosaccharomyces pombe

The cytoplasmic ribosomal proteins from a fission yeast Schizosaccharomyces pombe were analysed by two-dimensional polyacrylamide gel electrophoresis. Seventy-three protein species were identified in the 80S ribosome, and named SP-S1 to SP-S33 and SP-L1 to SP-L40 in the small and large subunits, respectively. Many of these proteins could be correlated to those of Saccharomyces cerevisiae on the basis of their electrophoretic mobilities. Eleven proteins were isolated from the 80S ribosome, and their amino acid compositions were determined. Of these, SP-S6, SP-L1, SP-L12, SP-L15, SP-L17, SP-L27, SP-L36 and SP-L40c and d were sequenced from their amino-termini. SP-S28 and SP-L2 appear to have their amino-termini blocked. These results were compared with the data available for the S. cerevisiae and rat liver ribosomal proteins. The S. cerevisiae counterparts of the eight proteins mentioned above were found to be YS4, YL1, YL10, YL14, YL35, YL40 and YL44c and d, respectively. The rat liver counterparts of SP-S6, SP-L1, SP-L27 and SP-L40c and d were the rat S6, L4, L37 and P2, respectively. Comparison of the partial sequences of these ribosomal proteins suggests that these two yeasts are relatively far apart, phylogenetically.     

Yeast ribosomal proteins. VIII. Isolation of two proteins and sequence characterization of twenty-four proteins from cytoplasmic ribosomes

Summary Two proteins, YL41 and YL43, were isolated from 80S ribosomes of Saccharomyces cerevisiae by filtration through a Sephacryl S-200 column and by chromatography on a column of carboxymethylcellulose. Their amino acid compositions are presented. Twenty-four proteins including these two proteins were subjected to sequence analyses by automated Edman degradation. Amino-terminal amino acid sequences were determined for 17 proteins, YS3, YS9, YS23, YS24, YS29, YL6, YL8, YL11, YL15, YL17, YL23, YL28, YL33, YL37, YL39, YL41, and YL43. YL41, which has a 72.7% lysine and arginine content, was found to be particular to eukaryotic ribosomes. The aminotermini of another seven proteins, YS2, YS5, YS8, YS12, YS13, YS20, and YS27, were suggested to be blocked.Comparison of the amino-terminal sequences with all other ribosomal protein sequences so far available indicates that YS9 shows sequence homology to rat liver ribosomal protein S8 (Wittmann-Liebold et al. 1979).     

Yeast motor proteins

Yeast accomplish a variety of intracellular motile events with the aid of mechanochemical enzymes known as motor proteins. This review covers the current state of knowledge on myosins, kinesins, dyneins, dynamins and SMC proteins present in yeast cells, and the most important developments in the study of yeast mitosis. Both topics have seen rapid progress over the past few years. Dedicated to Professor O. Nečas on the occasion of his 70th birthday     

Yeast ribosomal proteins: V. Correlation of several nomenclatures and proposal of a standard nomenclature

Summary A tentative nomenclature (YP number) for yeast (Saccharomyces cerevisiae) cytoplasmic ribosomal proteins, which is used in our laboratory (Otaka and Kobata 1978; Higo and Otaka 1979), has been correlated with those of Warner and Gorenstein (1978) and several others. Our nomenclature is based on the two-dimensional gel electrophoretic pattern of proteins as analyzed by a modified method of Mets and Bogorad (1974), while others have used various modifications of Kaltschmidt and Wittmann's two-dimensional gel electrophoresis (1970). The method of correlation involved the examination in our twodimensional electrophoresis system of each protein spot excised from gel patterns prepared by Kaltschmidt and Wittmann's method or vice versa.The numbers of protein species recognized in this paper are 29 for small subunit, and 44 for large subunit. Based on these results, we propose a standard nomenclature for yeast ribosomal proteins, in which the designations YS1–YS29 and YL1–YL44 have been given to the small subunit proteins and the large subunit proteins respectively.     

Yeast ribosomal P0 protein has two separate binding sites for P1/P2 proteins

The ribosome has a distinct lateral protuberance called the stalk; in eukaryotes it is formed by the acidic ribosomal P-proteins which are organized as a pentameric entity described as P0-(P1-P2)(2). Bilateral interactions between P0 and P1/P2 proteins have been studied extensively, however, the region on P0 responsible for the binding of P1/P2 proteins has not been precisely defined. Here we report a study which takes the current knowledge of the P0 - P1/P2 protein interaction beyond the recently published information. Using truncated forms of P0 protein and several in vitro and in vivo approaches, we have defined the region between positions 199 and 258 as the P0 protein fragment responsible for the binding of P1/P2 proteins in the yeast Saccharomyces cerevisiae. We show two short amino acid regions of P0 protein located at positions 199-230 and 231-258, to be responsible for independent binding of two dimers, P1A-P2B and P1B-P2A respectively. In addition, two elements, the sequence spanning amino acids 199-230 and the P1A-P2B dimer were found to be essential for stalk formation, indicating that this process is dependent on a balance between the P1A-P2B dimer and the P0 protein.     

The plastid-specific ribosomal proteins of Arabidopsis thaliana can be divided into non-essential proteins and genuine ribosomal proteins

Plastid translation occurs on bacterial-type 70S ribosomes consisting of a large (50S) subunit and a small (30S) subunit. The vast majority of plastid ribosomal proteins have orthologs in bacteria. In addition, plastids also possess a small set of unique ribosomal proteins, so-called plastid-specific ribosomal proteins (PSRPs). The functions of these PSRPs are unknown, but, based on structural studies, it has been proposed that they may represent accessory proteins involved in translational regulation. Here we have investigated the functions of five PSRPs using reverse genetics in the model plant Arabidopsis thaliana. By analyzing T-DNA insertion mutants and RNAi lines, we show that three PSRPs display characteristics of genuine ribosomal proteins, in that down-regulation of their expression led to decreased accumulation of the 30S or 50S subunit of the plastid ribosomes, resulting in plastid translational deficiency. In contrast, two other PSRPs can be knocked out without visible or measurable phenotypic consequences. Our data suggest that PSRPs fall into two types: (i) PSRPs that have a structural role in the ribosome and are bona fide ribosomal proteins, and (ii) non-essential PSRPs that are not required for stable ribosome accumulation and translation under standard greenhouse conditions.     

Phylogenic studies on ribosomal proteins

Two-dimensional electrophoresis of ribosomal proteins makes it possible to evaluate the phylogenic distance between any set of two species. The evaluation is based on the number of spots having the same electrophoretic mobility in the two species. The two-dimensional finger-prints of ribosomal proteins from mammals, reptiles and birds, which have diverged 300 million years ago, are identical. For more remote species with respect to mammals, the number of comigrating spots gradually decreases. For as remote species from mammals as plants, one third of the spots have still the same mobility. Only five proteins from E. coli comigrate with ribosomal protein from mammals. The low evolution of ribosomal proteins indicate the high degree of internal organization of the ribosome.