A class of soybean low molecular weight heat shock proteins : immunological study and quantitation

Two major polypeptides of the 15- to 18-kilodalton class of soybean (Glycine max) heat shock proteins (HSPs), obtained from an HSP-enriched (NH₄)₂SO₄ fraction separated by two-dimensional polyacrylamide gel electrophoresis, were used individually as antigens to prepare antibodies. Each of these antibody preparations reacted with its antigen and cross-reacted with 12 other 15- to 18-kilodalton HSPs. With these antibodies, the accumulation of the 15- to 18-kilodalton HSPs under various heat shock (HS) conditions was quantified. The 15- to 18-kilodalton HSPs began to be detectable at 35° C, and after 4 hours at 40° C they had accumulated to a maximum level of 1.54 micrograms per 100 micrograms of total protein in soybean seedlings and remained almost unchanged up to 24 hours after HS. Accumulation of the HSPs was reduced at temperatures higher than 40° C. At 42.5° C the HSPs were reduced to 1.02 micrograms per 100 micrograms, and at 45° C they were hardly detectable. A brief HS at 45° C (10 minutes), followed by incubation at 28° C, which also induced HSP synthesis, resulted in synthesis of this class of HSPs at levels up to 1.06 micrograms per 100 micrograms of total protein. Taking into consideration the previous data concerning the acquisition of thermotolerance in soybean seedlings, our estimation indicates that the accumulation of the 15- to 18-kilodalton HSPs to 0.76 to 0.98% of total protein correlated well with the establishment of thermotolerance. Of course, other HSPs, in addition to this group of proteins, may be required for the development of thermotolerance.     

Early and late heat shock proteins in wheats and other cereal species

Coleoptiles and roots of 3-day-old seedlings from five cereal species (Triticum aestivum L., T. durum Desf., Hordeum vulgare L., Secale cereale L., and Triticale) respond to heat shock at 40°C by synthesizing a new set of 13 strong bands (as revealed by one-dimensional sodium dodecyl sulfate gel electrophoresis) as well as some 20°C proteins. Heat shock proteins (HSPs) belong to three different size groups: high molecular mass HSPs in the 103 to 70 kilodalton range, intermediate molecular mass HSPs in the 62 to 32 kilodalton range, and low molecular mass HSPs about 17 to 16 kilodalton in size. At the beginning of the heat shock coleoptiles show a reduced ability to synthesize intermediate molecular mass HSPs but after 4 hours at 40°C they exhibit fully developed HSP patterns identical to that found in roots. Synthesis of early HSPs declines after 7 hours of treatment followed by the appearance of a new set of 12 protein bands (late HSPs) in the ranges 99 to 83, 69 to 35, and 15 to 14 kilodaltons. After 12 hours at 40°C, three other late HSPs of 89, 45, and 38 kilodalton are induced. The induction of late HSPs after 7 hours at 40°C appears to be associated with an enhancement of radioactive methionine incorporation into proteins.     

Identification and characterization of an immunologically conserved adenovirus early region 11,000 Mr protein and its association with the nuclear matrix

Antisera from some hamsters bearing adenovirus-induced tumors contain antibodies to an 11,000 M_r adenovirus-induced protein. In adenovirus-infected HeLa cells, this early viral protein was specifically associated with the nuclear matrix fraction. After two-dimensional gel electrophoresis, two forms of the 11,000 M_r protein at pI 5.6 and pI 5.4 were found. Only the pI 5.4 form of this protein was associated with the nuclear matrix fraction. Adenoviruses from groups A, B, C, D and E all produced an early viral protein (10,000 to 12,000 M_r) that reacted with group C antibody to the 11,000 M_r protein. To date, this is the only known early viral protein that is immunologically conserved in all of the human adenovirus groups.The positions of two methionine and seven leucine residues were determined by sequencing the first 35 amino acids from the N terminus of the adenovirus serotype 2 group C 11,000 M_r protein. The positions of these amino acid residues were compared to the adenovirus serotype 2 nucleotide sequence, which uniquely localized the structural gene of the 11,000 M_r protein to region E4, subregion 3 in type 2 adenovirus. A frameshift mutant, which contained a deletion of one base-pair in the structural gene of the 11,000 M_r protein, was isolated and mapped by marker rescue and nucleotide sequence analysis. This mutant failed to produce immunologically detectable 11,000 M_r protein. The mutant had a viable phenotype, producing normal levels of infectious virus in both HeLa cells and WI38 cells in culture. These experiments identify the first adenovirus early region 4 protein detected in virus-infected cells.     

Induction of freezing tolerance in spinach is associated with the synthesis of cold acclimation induced proteins

Spinach (Spinacia oleracea L. cv Bloomsdale) seedlings cultured in vitro were used to study changes in protein synthesis during cold acclimation. Seedlings grown for 3 weeks postsowing on an inorganic-nutrient-agar medium were able to increase their freezing tolerance when grown at 5°C. During cold acclimation at 5°C and deacclimation at 25°C, the kinetics of freezing tolerance induction and loss were similar to that of soil-grown plants. Freezing tolerance increased after 1 day of cold acclimation and reached a maximum within 7 days. Upon deacclimation at 25°C, freezing tolerance declined within 1 day and was largely lost by the 7th day. Leaf proteins of intact plants grown at 5 and 25°C were in vivo radiolabeled, without wounding or injury, to high specific activities with [³⁵S]methionine. Leaf proteins were radiolabeled at 0, 1, 2, 3, 4, 7, and 14 days of cold acclimation and at 1, 3, and 7 days of deacclimation. Up to 500 labeled proteins were separated by two-dimensional gel electrophoresis and visualized by fluorography. A rapid and stable change in the protein synthesis pattern was observed when seedlings were transferred to the low temperature environment. Cold-acclimated leaves contained 22 polypeptides not found in nonacclimated leaves. Exposure to 5°C induced the synthesis of three high molecular weight cold acclimation proteins (CAPs) (M_r of about 160,000, 117,000, and 85,000) and greatly increased the synthesis of a fourth high molecular weight protein (M_r 79,000). These proteins were synthesized during day 1 and throughout the 14 day exposure to 5°C. During deacclimation, the synthesis of CAPs 160, 117, and 85 was greatly reduced by the first day of exposure to 25°C. However, CAP 79 was synthesized throughout the 7 day deacclimation treatment. Thus, the induction at low temperature and termination at warm temperature of the synthesis of CAPs 160, 117, and 85 was highly correlated with the induction and loss of freezing tolerance. Cold acclimation did not result in a general posttranslational modification of leaf proteins. Most of the observed changes in the two-dimensional gel patterns could be attributed to the de novo synthesis of proteins induced by low temperature. In spinach leaf tissue, heat shock altered the pattern of protein synthesis and induced the synthesis of several heat shock proteins (HSPs). One polypeptide synthesized in cold-acclimated leaves had a molecular weight and net charge (M_r 79,000, pI 4.8) similar to that of a HSP (M_r 83,000, pI 4.8). However, heat shock did not increase the freezing tolerance, and cold acclimation did not increase heat tolerance over that of nonacclimated plants, but heat-shocked leaf tissue was more tolerant to high temperatures than nonacclimated or cold-acclimated leaf tissue. When protein extracts from heat-shocked and cold-acclimated leaves were mixed and separated in the same two-dimensional gel, the CAP and HSP were shown to be two separate polypeptides with slightly different isoelectric points and molecular weights.     

Pancreatic B-cells secrete a range of novel peptides besides insulin

Insulin secretion by a transplantable rat islet B-cell tumour is accompanied by the release of two putative proinsulin cleavage intermediates, four peptides of M_r 9000–12 000 (excluding proinsulin) and peptides of M_r 21 000, 34 000 and 60 000. Granule-enriched subcellular preparations contain major peptides of identical M_r values. Of these peptides seven at least coincide in molecular weight with peptides secreted by isolated rat islets and thus may be constituents of the normal insulin secretory granule.     

Expression of heat shock proteins in response to high and low temperature extremes in diapausing pharate larvae of the gypsy moth,Lymantria dispar

Diapausing pharate first instars of the gypsy moth, Lymantria dispar, respond to high temperature (37–41°C) by suppressing normal protein synthesis and synthesizing a set of seven heat shock proteins with M_rs of 90,000, 75,000, 73,000, 60,000, 42,000, 29,000, and 22,000 as determined by SDS-PAGE. During recovery at 25°C from heat shock, synthesis of the heat shock proteins gradually decreases over a period of 6 h, while normal protein synthesis is restored. A subset of these same heat shock proteins is also expressed during recovery at 4°C or 25°C from brief exposures to low temperature (-10 to 20°C), and its expression is more intense with increased severity of cold exposure. During recovery at 4°C after 24 h at ?20°C, both 90,000 and 75,000 M_r heat shock proteins are expressed for more than 96 h. While normal protein synthesis is suppressed during heat shock and recovery from heat shock, normal protein synthesis coincides with synthesis of the heat shock proteins during recovery from low temperatures, thus implying that expression of the heat shock proteins is not invariably linked to suppression of normal protein synthesis. Western transfer, using a monoclonal antibody that recognizes the inducible form of the human 70,000 M_r heat shock protein, demonstrates that immunologically related proteins in the gypsy moth are expressed at 4°C and during recovery from cold and heat shock.     

Purification and molecular properties of 3 polypeptides released from a highly active O2-evolving photosystem-II preparation by Tris-treatment

Tris-treatment of a highly active O₂-evolving photosystem-II preparation induced release of 3 polypeptides (M_r 33 000, 24 000 and 18 000), concomitant with inhibition of O₂ evolution [FEBS Lett. (1981)_133. 265-268]. The 3 polypeptides were purified with the use of electrofocusing. Isoelectric points of the proteins were 5.1, 6.5 and 9.2 in order of decreasing M_r value. Only a trace amount of histidine, cystein and methionine were detected in these proteins. Based on the amino acid compositions, polarity indexes of the proteins were calculated to be 47–49%, suggesting the 3 proteins to be hydrophilic.     

Molecular weights of glycollate oxidase from C3 and C4 plants determined during early stages of purification

The M_rs of glycollate oxidase (EC 1.1.3.1) (GAO) determined soon after extraction from the leaves of several C₃ and C₄ plants are reported. The enzyme isolated from the C₃ plants wheat, barley, spinach, pea and tobacco has M_r in the range 160–180 000 and is probably a homotetramer. GAO purified from pea was previously reported as a dimer and as an octamer from spinach leaves. Therefore the quaternary structure of these GAOs soon after extraction differs from that of the purified proteins. The enzymes from the C₄ plants maize and sugar cane have M_rs ca twice this value in the range 290–310 000, whilst that of the C₄ grass Panicum maximum has an M_r of 162 000. An improved spectrophotometric assay for GAO, using a non-carcinogenic dye, is described.     

Isolation and characterization of the outer membrane of Acinetobacter calcoaceticus

A method for the separation of the outer membrane (OM) from the cytoplasmic membrane (CM) of Acinetobacter calcoaceticus 69/V grown on different carbon sources is described. The contamination of the OM with CM was less than 10%. Independent of the carbon source, five protein bands with apparent molecular weights of 47 000, 33000, 21 000, 19 000 and 12 000 were found by solubilization at 37°C and six bands at 100°C (apparent M_r 53 000, 47 000, 38 000, 26 000, 21000, 12000). Three proteins were modifiable by heat. With the periodic acid-Schiff procedure the bands with apparent M_r of 33 000 and 12 000 were made visible. After growth on d,l-carnitine an additional two non-heat-modifiable protein bands with apparent M_r between 40 000 and 45 000 were detected. By cultivation on acetate and peptone as carbon source one additional band (M_r 15 000) from OM of cells could be found.     

Effect of estrogen-treated porcine ampulla oviductal epithelial cells on early embryonic development in vitro and characterization of their protein synthetic activity

Recent studies by Buhi et al. have demonstrated that estrogen (E₂) is responsible for the induction of de novo synthesis and secretion of certain oviductal secretory proteins (OSP) and inhibition of other OSP in porcine oviductal explant cultures. The present work was undertaken to evaluate the effect of E₂-treated oviductal epithelial cell coculture on the development of early porcine embryos derived from in vitro matured and fertilized oocytes. In vitro synthesis of secretory proteins by E₂-treated oviductal cells used for coculture was also investigated by one-dimensional (1D) and two-dimensional (2D) sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE). The results showed that the cleavage rate was significantly enhanced by coculturing fertilized eggs with E₂-treated oviductal epithelial cells. The in vitro protein synthetic pattern of oviductal secretory proteins was influenced by E₂ treatment. These variations included the disappearance of one protein (82 000 M_r) and the appearance of another (33 000 M_r) in the E₂-treated group as assessed by 1D-SDS-PAGE. Additional proteins of M_r 97 000 and an M_r 36 000–45 000 complex were increased in abundance by the E₂ treatment. Analyses by 2D-SDS-PAGE revealed three major E₂-dependent proteins, of M_r 45 000 (pI 5.5), 43 000 (pI 5.5) and a 36 000–45 000 M_r (pI 4.8) protein complex, whereas polypeptides of M_r 97 000 (pI 5.1), 36 000 (pI 8.0) and 25 000 (pI 6.8) were inhibited by E₂ treatment. The results demonstrated that porcine epithelial cell protein synthetic patterns are influenced by E₂ treatment and that estradiol treatment of oviductal cells may increase the rate of zygote cleavage during early development in vitro in pigs.     

Characterization of the heat shock response in cultured sugarcane cells : I. Physiology of the heat shock response and heat shock protein synthesis

Effect of heat shock on the growth of cultured sugarcane cells (Saccharum officinarum L.) was measured. Heat shock (HS) treatment at 36 to 38°C (2 hours) induced the development of maximum thermotolerance to otherwise nonpermissive heat stress at 54°C (7 minutes). Optimum thermotolerance was observed 8 hours after heat shock. Development of thermotolerance was initiated by treatments as short as 30 minutes at 36°C. Temperatures below 36°C or above 40°C failed to induce maximum thermotolerance. In vivo labeling revealed that HS at 32 to 34°C induced several high molecular mass heat shock proteins (HSPs). A complex of 18 kilodalton HSPs required at least 36°C treatment for induction. The majority of the HSPs began to accumulate within 10 minutes, whereas the synthesis of low molecular mass peptides in the 18 kilodalton range became evident 30 minutes after initiation of HS. HS above 38°C resulted in progressively decreased HSP synthesis with inhibition first observed for HSPs larger than 50 kilodaltons. Analysis of two-dimensional gels revealed a complex pattern of label incorporation including the synthesis of four major HSPs in the 18 kilodalton range and continued synthesis of constitutive proteins during HS.     

Different intracellular distributions of heat-shock and arsenite-induced proteins in Drosophila Kc cells. Possible relation with the phosphorylation and translocation of a major cytoskeletal protein

The intracellular distribution of heat shock proteins (hsps) from Drosophila Kc cells is different in heat and in arsenite-treated cells. While the cytoplasmic localization of hsp 84 is confirmed in both treatments, the association of hsp 70 with the nucleus occurs only in heat-treated cells. This heat-dependent association of certain hsps with the nuclear pellet is confirmed by incubation of cells at various temperatures ranging from 23 to 39 °C. Furthermore their presence in this nuclear pellet can be correlated with the translocation and phosphorylation of a major cellular cytoskeletal protein of M_r 45,000. It is concluded that the previously reported nuclear association of hsps is not necessarily indicative of a nuclear function. It is further suggested that hsps might have a structural function within the cell.     

Simultaneous preparation of the three biotin-containing mitochondrial car☐ylases from rat liver

Affinity chromatography on avidin-Sepharose column was used to bind the biotin-containing car?ylases from rat liver. With a biotin gradient (0–0.3 mM), peaks of activity of pyruvate, propionyl CoA and β-methylcrotonyl CoA car?ylases co-eluted. Subsequent separation of the three car?ylases was attained using DEAE-Sepharose chromatography. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed each of the enzymes to be pure, with pyruvate car?ylase giving a single subunit band (M_r 130 000), propionyl-CoA car?ylase giving two bands (M_r 73 000and56500) and β-methylcrotonyl-CoA car?ylase giving two bands (M_r 75 000and60 000. The specific activity of propionyl-CoA car?ylase (15.8 munits/mg) and β-methylcrotonyl-CoA car?ylase (24.2 munits/mg) were comparable with reported activities for these purified enzymes, while that of pyruvate car?ylase (1.25 munits/mg) was low. This is a suitable method for the simultaneous preparation of purified car?ylases for the specific purpose of raising antisera to these enzymes.     

Cloning, sequence analysis, and expression of a cDNA encoding a plastid-localized heat shock protein in maize

We have cloned and characterized a cDNA encoding a maize (Zea mays L.) heat shock protein (HSP), HSP26. The mRNA of HSP26 is present as a single mRNA species of 1.1 kilobase pairs in size and is detectable when maize seedlings are treated at 40°C but not at 28°C. Accumulation of HSP26 mRNA was detected after 10 minutes of incubation at 40°C, reaching the maximum level after 1 hour. Comparison of the deduced amino acid sequence of maize HSP26 to other HSPs indicated a strong homology to the sequences of two nuclear encoded HSPs that are transported into the chloroplasts during heat shock: pea HSP21 and soybean HSP22. Maize HSP26 was also found to cross-react with anti-pea chloroplast HSP21 antibodies. Because of the sequence homology between maize HSP26, soybean HSP22, and pea HSP21, in vitro chloroplast protein import experiments were conducted. The in vitro synthesized maize HSP26 is specifically imported to the soluble fraction of the chloroplast and processed to a smaller polypeptide. The sequence homology and antibody cross-reactivity between maize HSP26 and pea HSP21 have allowed us to conclude that maize HSP26 is a nuclear-encoded, plastid-localized protein in maize.     

Heat Shock Inhibits alpha-Amylase Synthesis in Barley Aleurone without Inhibiting the Activity of Endoplasmic Reticulum Marker Enzymes

The effects of heat shock on the synthesis of α-amylase and on the membranes of the endoplasmic reticulum (ER) of barley (Hordeum vulgare) aleurone were studied. Heat shock, imposed by raising the temperature of incubation from 25°C to 40°C for 3 hours, inhibits the accumulation of α-amylase and other proteins in the incubation medium of barley aleurone layers treated with gibberellic acid and Ca²⁺. When ER is isolated from heat-shocked aleurone layers, less newly synthesized α-amylase is found associated with this membrane system. ER membranes, as indicated by the activities of NADH cytochrome c reductase and ATP-dependent Ca²⁺ transport, are not destroyed by heat stress, however. Although heat shock did not reduce the activity of ER membrane marker enzymes, it altered the buoyant density of these membranes. Whereas ER from control tissue showed a peak of marker enzyme activity at 27% to 28% sucrose (1.113-1.120 grams per cubic centimeter), ER from heat-shocked tissue peaked at 30% to 32% sucrose (1.127-1.137 grams per cubic centimeter). The synthesis of a group of proteins designated as heat-shock proteins (HSPs) was stimulated by heat shock. These HSPs were localized to different compartments of the aleurone cell. Several proteins ranging from 15 to 30 kilodaltons were found in the ER and the mitochondrial/plasma membrane fractions of heat-shocked cells, but none of the HSPs accumulated in the incubation medium of heat-shocked aleurone layers.     

Purification and characterization of two essential cytochromes of the thiosulphate-oxidizing multi-enzyme system from Thiobacillus A2 (Thiobacillus versutus)

Four c-type cytochromes were purified by several procedures including chromatography on DEAE-Sepharose CL-6B, Phenyl-Sepharose CL-4B and Sephadex G-75, G-100 and G-200 and chromatofocusing. Cytochrome c-551 had a pI value of 5.2 and an M_r of 260 000 consisting of six non-covalently bound polypeptides each with an M_r of 43 000, and contained four to five haems. Cytochrome c-552.5 had a pI value of 4.8 and an M_r of 56 000 consisting of two polypeptides with the same M_r 29 000, and contained two haems. Cytochromes c-551 and c-552.5 were reduced by ascorbate to about 70 and 60% of the fully dithionite-reduced values, respectively, and both were essential components in the thiosulphate-oxidizing multi-enzyme system (other components of the system were ‘enzyme A’, ‘enzyme B’ and sulphite: cytochrome c oxidoreductase). These two cytochromes functioned as electron carriers and effectors in the oxidation of thiosulphate. Some evidence suggested that cytochrome c-551 might be a specialized electron transfer component for sulphonate-sulphur oxidation. Both cytochromes could be reduced by thiosulphate in the presence of enzymes A and B. Cytochrome c-550 (basic) and cytochrome c-550 (acidic) were small proteins with M_r 15 000 and 14 000 and pI values of over 8 and 5, respectively. Their physiological role is uncertain.     

The purification and partial amino acid sequence of a polypeptide from the glutelin fraction of rice grains; homology to pea legumin

The glutelin fraction was extracted from grain meals of rice (Oryzea sativa) with 50 mM Tris-HCl buffer (pH 8.8) containing 6 M urea and 10 mM 2-mercaptoethanol. Polypeptides of glutelin were separated and purified by ion-exchange chromatography under denaturing conditions. Analysis by two-dimensional gel electrophoresis showed that 2 major polypeptides of the rice glutelin fraction, M_r 36 000 and 22 000, were linked in disulphide bonded pairs containing one M_r 36 000 and one M_r 22 000 subunit. A partial amino acid sequence of the purified M_r 22 000 glutelin subunit showed it to be homologous to the β-subunit of pea legumin, a storage protein which also contains disulphide-linked subunit pairs (M_r 38 000 and M_r 22 000). It is therefore proposed that the major component of rice glutelin is a legumin-like protein.     

Sequence interrelationships of the subunits of vicilin from pea seeds

Serological studies and comparison of N-terminal amino acid sequences with the amino acid sequence deduced from a cDNA clone have been used to establish the sequence relationships between the subunits of the pea seed storage protein, vicilin. Subunits smaller than M_r～50 000 (i.e., M_r 34 000, 30 000, 25 000, 18 000, 14 000, 13 000 and 12 000) show extensive homology with molecules within M_r～50 000 group. Both the sequencing and serological data confirm earlier evidence from studies on vicilin synthesisin vivo andin vitro which indicated that the vicilin subunits smaller than M_r～50 000 arose by endoproteolytic cleavage of parent molecules within the M_r～50 000 group. Cleavage in different M_r 50 000 parent molecules containing either one or both of two susceptible processing sites accounts for the formation of all the vicilin subunits smaller than M_r～50 000, with the possible exception of the M_r34 000 polypeptide. The position of these sites in the putative parents were defined by reference to a complete amino acid sequence deduced from the sequence of DNA complementary to mRNA for one member of the M_r～50 000 group.