Characterization of two acidic proteins of Saccharomyces cerevisiae ribosome

In $\text{Saccharomyces}\text{cerevisiae}$ ribosomes two proteins, L44 and L45, of strong acidic character are detected. These proteins, presumably equivalent to bacterial L7 and L12, have been purified and have given a total cross reaction when tested by double immunodiffusion. Reaction with fluorescamine has shown that the amino terminal group of the polypeptide is blocked in protein L44 and free in protein L45. Tryptic analysis of the two proteins shows that three out of nine peptides are in identical position in both patterns, three more are easily related and the last three are clearly different. The data indicate that proteins L44 and L45 are closely related but not totally identical.     

Analysis of kethoxal bound to ribosomal proteins from Escherichia coli 70S reacted ribosomes

To investigate ribosome topography and possible function, 70S ribosomes of $\text{Escherichia coli}$ were reacted with the dicarbonyl compound kethoxal. Ribosomal protein was extracted after reaction, and through two dimensional gel electrophoresis, the reactive proteins of the two subunits were identified. From the 30S subunit, the most reacted proteins were S2, S3, S4, S5 and S7 and from the 50S subunit, L1, L5, L16, L17, L18 and L27. The results with kethoxal are compared with other modifiers of ribosomal proteins.     

Ribosomal protein as substrate for a GTP-dependent protein kinase from yeast

A protein kinase specific for casein and acidic ribosomal proteins was isolated and partly characterized.It was found that the enzyme utilizes GTP and ATP as phosphoryl donors. Its affinity for ATP was considerably higher than for GTP with the km values of 7.6 × 10^-6M and 5.5 × 10^-5M, respectively.Two-dimensional acrylamide gel electrophoresis revealed the phosphorylation of the same ribosomal proteins with either of the [-³²P] nucleotides used. It was also shown that one acidic protein (S1 or S2) of 40 S and two acidic proteins (L2 and L3) of 60 S ribosomal subunits were predominantly phosphorylated in vitro. The phosphorylated proteins: L2 and L3 seem to correspond to the proteins of L7 and L12 of E. coli ribosomes. The isolated kinase phosphorylated several basic ribosomal proteins though to a lower extent than the acidic ones.     

Two-dimensional separation of chloroplast membrane proteins by isoelectri focusing and electrophoresis in sodium dodecyl sulphate

Proteins of chloroplast subfragments enriched in Photosystem I and Photosystem II electron flow activity have been analyzed by two-dimensional polyacrylamide gel electrophoresis. In the first dimension, polyacrylamide gel isoelectric focusing (pH 5–7) was used in the presence of Triton X-100, followed at right angle by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. Characteristic fingerprints were obtained for the Photosystem I and II fractions and a correlation between the major proteins separated by isoelectric focusing and the major polypeptides separated by undimensional SDS electrophoresis was established. Two dominant spots of 68 000 and 60 000 daltons appeared in the two-dimensional patterns of Photosystem I fractions $\text{p}\text{I}$ values about 5.6; two spots with molecular weights of 33 000 and 23 000 were characteristics for Photosystem II fractions $\text{p}\text{I}$ values about 5.3 and 6.3). Photosystem I fractions were furthermore characteristics by a series of spots in the 44 000–33 000 range $\text{p}\text{I}$ values from about 5.9 to 6.8). The two-dimensional system revealed that (a) several SDS-polypeptides have multiple forms differing in charge only, (b) some proteins separated by isoelectric focusing are resolved in the second dimensional into polypeptides of different size. The two-dimensional method combining Triton X-100 isoelectric focusing' and SDS electrophoresis provides a higher degree of resolution than either of the unidimensional methods thus allowing a detailed analysis of chloroplast membrane proteins.     

A complex of acidic ribosomal proteins. Evidence of a four-to-one complex of proteins in the Bacillus stearothermophilus ribosome

Two acidic proteins from the 50 S subunit of Bacillus stearothermophilus ribosomes, namely B-L13 (homologous to Escherichia coli protein $\text{L}\text{7}\text{L}\text{12}$) and B-L8, form a complex. Radioactive B-L13, added to ribosomes before dissociation, does not appear in the complex after electrophoresis, so the (B-L13 · B-L8) complex must exist in the ribosome before dissociation. Digestion of B. stearothermophilus ribosomes with polyacrylamide-bound trypsin causes the appearance of new B-L8 and B-L13 spots on two-dimensional polyacrylamide gel electrophoresis, in a pattern which suggests that single molecules of B-L13 are being sequentially cleaved from a four-to-one complex of B-L13 and B-L8.     

U.V. induced covalent crosslinking of E.coli ribosomal RNA to specific proteins

$\text{E.}\text{coli}$ 70S ribosomes uniformly labeled $\text{in}\text{vivo}$ with ³²PO₄ were subjected to varying doses of u.v. radiation and then to the combined action of the RNases A and T₁. Following these treatments the ribosomal proteins were separated by trichloroacetic acid precipitation from the noncovalently attached RNA degradation fragments. Subsequent two-dimensional gel electrophoresis and autoradiography of these proteins revealed that significant ³²PO₄ was associated with unique ribosomal proteins, L2 was among these.     

Gel electrophoretic studies on ribosomal proteins L7L12 and the Escherichia coli 50 s subunit

Three forms of the 50 S ribosomal subunit of Escherichia coli have been separated by agarose/acrylamide gel electrophoresis. The slowest migrating form, S-50 S, corresponded to native 50 S subunits and contained four copies of proteins $\text{L}\text{7}\text{L}\text{12}$. Removal of the four copies of this protein produced a more rapidly migrating form, M-50 S. The M-50 S form was then converted to the fastest migrating form, F-50 S, by removal of additional proteins, including L10 and L11. A one-step removal of a pentameric complex of four copies of $\text{L}\text{7}\text{L}\text{12}$ plus L10 converted the S-50 S subunit directly to the F-50 S subunit. These proteins recombined specifically with the appropriate protein-deficient 50 S subunit at 3 °C to reform the S-50 S subunit, i.e. the M-50 S subunit was converted back to the S-50 S form by the addition of purified proteins $\text{L}\text{7}\text{L}\text{12}$; and the F-50 S subunit bound the pentameric complex of $\text{L}\text{7}\text{L}\text{12}$ and L10 to form S-50 S. The binding of the pentameric complex, isolated by glycerol gradient centrifugation, supports the model that all four copies of proteins $\text{L}\text{7}\text{L}\text{12}$ are together in one part of the ribosome called the “$\text{L}\text{7}\text{L}\text{12}$ stalk”. Only the four copies of $\text{L}\text{7}\text{L}\text{12}$ were removed from the 50 S subunit in low salt (0.125 m-NH₄Cl) plus 50% ethanol at 0 °C. These ribosomes (in the M-50 S form) had less than 5% of the peptide-synthesizing activity of untreated control ribosomes as measured by a poly(U) translation system in vitro. Peptide-synthesizing activity was restored, upon addition of $\text{L}\text{7}\text{L}\text{12}$, back to the treated ribosomes to give 50 S subunits (S-50 S) with a full complement of four copies of $\text{L}\text{7}\text{L}\text{12}$. Antibody to proteins $\text{L}\text{7}\text{L}\text{12}$ bound only to the S-50 S subunits, producing four new bands separated by gel electrophoresis. The bands represented complexes of one, two, three and four antibodies bound to a 50 S subunit. This result was obtained using either 50 S subunits or 70 S tight couples and indicated that all four copies of $\text{L}\text{7}\text{L}\text{12}$ are either located at a single site in the $\text{L}\text{7}\text{L}\text{12}$ stalk or, much less likely, are divided between two symmetrical sites. Proteins $\text{L}\text{7}\text{L}\text{12}$ were not only accessible to their specific antibody but could also be removed from 70 S ribosomes and polyribosomes without causing their dissociation into subunits. The ribosomes and polyribosomes had an increased gel electrophoretic mobility which was reversed by addition of proteins $\text{L}\text{7}\text{L}\text{12}$.     

Structural alteration of rRNA in the L7/L12 region of 50s ribosome on removal of L7/L12 proteins

Core particles of 50S ribosomes depleted of $\text{L7}\text{L12}$ proteins are degraded by RNase I at a considerably slower rate than intact 50S ribosomes. The normal rate is restored on incorporating $\text{L7}\text{L12}$ proteins into the core particles. The capacity of the core particles to inhibit the RNase I-catalyzed hydrolysis of poly A and to bind ethidium bromide is also greater with core particles than with intact 50S ribosomes. It appears from these results that the region(s) of rRNA in the vicinity of $\text{L7}\text{L12}$ proteins has less ordered structure which, on removal of $\text{L7}\text{L12}$ proteins, becomes more organized. Apparently, binding of $\text{L7}\text{L12}$ proteins to the 50S core leads to the destabilization of double-stranded regions of rRNA.     

Phosphorylation of nonhistone chromatin proteins during sea urchin development

The phosphorylation of nonhistone chromatin proteins during development was studied in the sea urchin, $\text{Strongylocentrotus purpuratus}$. The rate of phosphorylation was found to be maximal during gastrula, slightly lower during prism and almost 70% lower in pluteus stage embryos. Analysis of the phosphorylated nonhistone chromatin proteins by SDS-acrylamide gel electrophoresis showed significant variations in the labeling pattern during different stages of development. A specific protein which is actively phosphorylated during gastrula and prism stages is nearly absent from the pluteus stage.     

Saccharomyces cerevisiae killer expression mutant kex2 has altered secretory proteins and glycoproteins.

The extracellular proteins and glycoproteins of a yeast mutant $\text{kex}\text{2–15}$ defective in killer toxin expression were separated by one and two dimensional polyacyylamide gel electrophoresis. Many mutant extracellular proteins and glycoproteins show both altered electrophoretic mobility and isoelectric points when compared with the parent strain. Altered proteins and glycoproteins from $\text{kex}\text{2–15}$ were identified with their parental counterparts by peptide mapping. The observed alterations co-segregated with the $\text{kex}\text{2}$ nuclear mutation in genetic crosses.     

The presence of multiple cytochrome b proteins in succinate-cytochrome c reductase.

Two cytochrome $\text{b}$ proteins were isolated from succinate-cytochrome $\text{c}$ reductase and the cytochrome $\text{b-c}{}_1$ complex. Their molecular weights were determined to be 37,000 and 17,000 daltons by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Spectral properties and amino acid composition of these two proteins are reported in the paper.     

A method for extracting intact chloroplast and cytoplasmic ribosomal RNA from leaves

A method is described for extracting intact chloroplast and cytoplasmic ribosomal RNA from leaves of two higher plant species. Sodium dodecyl sulfate (1%) and 25 mM magnesium ions are required to inhibit ribonuclease action during RNA purification by phenol deproteinization. The ethanol-precipitated RNA product, including 23s chloroplast ribosomal RNA, is completely stable during electrophoresis in the absence of magnesium ions, even in the presence of EDTA. The $\text{in}$$\text{vivo}$ mole fraction of chloroplast ribosomes relative to cytoplasmic ribosomes is estimated. Bentonite is shown to cause preferential losses of chloroplast RNA during extraction.     

Identification of ubiquinone binding proteins in ubiquinol-cytochrome c reductase by arylazido ubiquinone derivative

A functionally active $\text{arylazido-1-[}{}^{14}\text{C]-β-alanine}$ ubiquinone derivative has been synthesized for the identification of the ubiquinone binding protein in ubiquinol-cytochrome $\text{c}$ reductase. After photolysis, the ¹⁴C activity was found to be specifically associated to proteins with mobilities relative to cytochrome $\text{c}$ of 0.841 and 0.475 in the sodium dodecylsulfate polyacrylamide gel electrophoresis of the Weber and Osborn system. These two proteins have previously been identified as $\text{b}$ cytochromes. The ¹⁴C activity distribution pattern was observed to be identical in the presence or absence of phospholipids during the photolysis. Antimycin A also produces no change in the ¹⁴C activity distribution among the proteins of this enzyme complex.     

The abnormal phosphorylation of spectrin in human hereditary spherocytosis

The phosphorylation of the proteins of the erythrocyte membrane of patients suffering from hereditary spherocytosis is investigated in intact erythrocytes by their incubation in the presence of radioactive inorganic phosphate. Examination of the phosphorylated components by high-resolution two-dimensional gel electrophoresis reveals only one defect in the pathological membranes, a depressed phosphorylation of the smaller polypeptide of spectrin; band 2. The phosphorylation of band 2 is measured with reference to the phosphorylation of syndein ($\text{2.1 + 2.2 + 2.3}$). In patients showing overt clinical symptoms and for whom splenectomy is advocated the phosphorylation of band 2 is depressed by approx. 70%. After splenectomy the phosphorylation of membrane proteins is restored to normal levels.     

The presence of two major protein components in the bovine photoreceptor disc membrane.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of thoroughly washed rod outer segment membrane preparations from bovine retinae revealed two major membrane-bound components and not one as has been generally thought. The higher molecular weight peak (?38500 molecular weight) contains a carbohydrate component and is covalently bound to the retinylidene chromophore. Moreover, this material is extensively phosphorylated $\text{in vitro}$ upon illumination. Therefore, this component (peak H) is rhodopsin. The nature and function of the other photoreceptor disc membrane component (peak L, ?34500 molecular weight) remains to be determined.     

Identification of an Escherichia coli inner membrane polypeptide specified by a lambda-tonB transducing.

Analysis by polyacrylamide gel electrophoresis of the proteins coded by a λ$\text{ton}$B transducing phage, after infection of UV-irradiated bacteria, revealed the presence of at least 7 new polypeptides. Three of these were identified as proteins of the $\text{trp}$ operon whilst three others were deleted by a spontaneous mutation in the $\text{ton}$B region carried by the phage. A single polypeptide, molecular weight 40,000 was absent from a phage carrying a proflavine induced mutation in $\text{ton}$B. We conclude that this protein, which was localised in the inner membrane by sarkosyl fractionation of the envelope, is the $\text{tonB}$ product.     

Dephosphorylation of 40S ribosomal subunits by phosphoprotein phosphatase activity from rabbit reticulocytes.

Phosphoprotein phosphatase activities which remove phosphoryl groups from ribosomal protein have been partially purified from rabbit reticulocytes by chromatography on DEAE-cellulose. Two major peaks of phosphoprotein phosphatase activity were observed when 40S ribosomal subunits, phosphorylated $\text{in vitro}$ with cyclic AMP-regulated protein kinases and (γ-³²P)ATP, were used as substrate. The phosphatase activity eluting at 0.14 M KCl was characterized further using ribosomal subunits phosphorylated $\text{in situ}$ by incubation of intact reticulocytes with radioactive inorganic phosphate. Phosphate covalently bound to 40S ribosomal subunits and 80S ribosomes was removed by the phosphatase activity. The enzyme was not active with phosphorylated proteins associated with 60S ribosomal subunits.     

Increased synthesis of a low molecular weight protein in vincristine-resistant cells

A 19,000-dalton peptide (pI = 5.7) that is synthesized in increased amounts in vincristine-resistant Chinese hamster cells ($\text{DC-3F}\text{VCRd-5}$) has been identified by two-dimensional gel electrophoresis. Reduced amounts of the protein were present in a revertant line of $\text{DC-3F}\text{VCRd-5}$, and only trace amounts were detected in control DC-3F cells. A similar protein (M_r = 19,000; pI = 5.7) was also found in a vincristine-resistant mouse line. Two vincristine-resistant human neuroblastoma cell lines likewise contained elevated levels of a low molecular weight acidic protein. Increased biosynthesis of the 19,000-dalton polypeptide in $\text{DC-3F}\text{VCRd-5}$ cells coincides with the presence of a homogeneously staining region, HSR, on a metaphase chromosome.     

Cross-linking studies on a cytochrome c-cytochrome c oxidase complex.

A cytochrome $\text{c}$ - cytochrome $\text{c}$ oxidase complex containing 0.8–1.0 moles of cytochrome $\text{c}$ per mole of cytochrome $\text{c}$ oxidase (heme a + a₃) was isolated as described by Ferguson-Miller, S., Brautigan, D.L., and Margoliash E., J. Biol. Chem. $\text{251}$, 1104 (1976). This complex was reacted with dithiobissuccinimidyl propionate, an 11 Å bridging bifunctional reagent, and the cross-linked products obtained were analyzed by two dimensional gel electrophoresis. Cytochrome $\text{c}$ was cross-linked to subunit II of cytochrome $\text{c}$ oxidase. Other cross-linked products were formed involving different subunits of cytochrome $\text{c}$ oxidase. These included I+V, II+V, III+V, V+VII, IV+VI and IV+VII. Experiments are also described using N,N′-bis(3-succinimidyloxycarbonylpropyl) tartarate. The major product formed with this 18 Å bridging bifunctional reagent was a pair containing II+VI.     

Stoichiometric analysis of barley plastid ribosomal proteins

We analyzed the protein composition of plastid 70S ribosomes isolated from the stromal fractions of barley plastids by the radical-free and highly reducing method of two dimensional polyacrylamide gel electrophoresis (RFHR 2D-PAGE). Intactness of the ribosomes was confirmed by the poly(U)-directed phenylalanine polymerization activity and by the reassociation capacity of the subunits into 70S ribosomes. The small and large ribosomal subunits were composed of 23 and 36 proteins, respectively. In addition, one acidic protein associated with ribosomes in low salt buffer but released in high salt buffer was found. The plastid ribosomes contained relatively larger numbers of acidic proteins than prokaryotic ribosomes. Stoichiometric analysis revealed the presence of several ribosomal proteins in low copy numbers, indicating that the ribosomes of plastids were heterogeneous. We also investigated the protein composition of plastid ribosomes from greening barley leaves and found that it did not change during greening.