Synthesis of the low molecular weight heat shock proteins in plants

Heat shock of living tissue induces the synthesis of a unique group of proteins, the heat shock proteins. In plants, the major group of heat shock proteins has a molecular mass of 15 to 25 kilodaltons. Accumulation of these proteins to stainable levels has been reported in only a few species. To examine accumulation of the low molecular weight heat shock proteins in a broader range of species, two-dimensional electrophoresis was used to resolve total protein from the following species: soybean (Glycine max L. Merr., var Wayne), pea (Pisum sativum L., var Early Alaska), sunflower (Helianthus annuus L.), wheat (Triticum aestivum L.), rice (Oryza sativa L., cv IR-36), maize (Zea mays L.), pearl millet (Pennisetum americanum L. Leeke, line 23DB), and Panicum miliaceum L. When identified by both silver staining and incorporation of radiolabel, a diverse array of low molecular weight heat shock proteins was synthesized in each of these species. These proteins accumulated to significant levels after three hours of heat shock but exhibited considerable heterogeneity in isoelectric point, molecular weight, stainability, and radiolabel incorporation. Although most appeared to be synthesized only during heat shock, some were detectable at low levels in control tissue. Compared to the monocots, a higher proportion of low molecular weight heat shock proteins was detectable in control tissues from dicots.     

Synthesis of low molecular weight mimetics of heparin

Natural hexosaminoglycan heparin remains the most commonly prescribed anticoagulant in hospitalized patients. However its administration could induce side clinical events, including thrombocytopenia and bleeding. This explaines the need of development of alternative anticoagulant drugs based on modified heparin and polyanionic oligo- and polysaccharide derivatives, such as sulfated glucans, phosphomannans and fucoidans. Here we review the works on the synthesis of oligosaccharides related to low molecular weight hepain fragments and their derivatives, as well as oligosaccharides, which imitate parts of heparin chain responsible for biological activity. These works were aimed to develop the pharmaceutical preparations lacking ofheparin disadvantages.     

Difference sedimentation velocity adapted to low molecular weight proteins

The difference sedimentation velocity technique reported by Kirschner and Schachman (1971, Biochemistry10, 1900–1919) has been modified to eliminate the need for a supernatant region. The method is now applicable to the measurement of small changes in sedimentation coefficient for low molecular weight proteins and other small macromolecules. Procedural changes necessary to overcome the absence of a supernatant region until late in the run have been devised and tested. A modified double-sector centerpiece was used to match the radial positions of the two menisci. The integration of the moment of the concentration difference was carried out from the meniscus to the plateau region, rather than over the peak only. The interference baseline was measured on photographs at the start of each run and after remixing. Some instability of baseline height was noted. The calculation method adjusted the baseline height to correspond with the concentration difference in the plateau region arising from unequal radial dilution. Tests of the method have been made using D₂O to retard the sedimentation of lysozyme. The interference results at low D₂O concentration (small values of Δs) are in agreement with schlieren results at high D₂O concentrations. Changes of 0.005 S have been detected.     

New pepsin-solubilized low molecular weight collagenous component possibly unique to periodontal ligament

Limited pepsin digestion of bovine periodontal ligament releases genetic types I, III, and V collagen and a high cystine containing low molecular weight collagenous component. Salt fractionation and molecular sieve chromatography allowed the isolation of the latter as an apparently pure homogeneous moiety which had an approximate molecular mass of 30 000 daltons. Reduction with mercaptoethanol yielded a single 10 000-dalton band on polyacrylamide gel electrophoresis in sodium dodecyl sulfate. This led us to conclude that the newly isolated low molecular weight collagen fragment consists of three similar molecular weight chains. Unreduced collagen-like glycoprotein (CGP) [Jander, R., Troyer, D., & Rauterberg, J. (1984) Biochemistry 23, 3675-3681] after extraction from tissues with collagen denaturing solvents yields the GP140 glycoprotein upon reduction and does not release any collagen fragment below 90 000 daltons upon mild or vigorous pepsin digestion. The GP140 glycoprotein [Heller-Harrison, R. A., & Carter, W. G. (1984) J. Biol. Chem. 259, 6858-6864] isolated by extraction under reducing and collagen denaturing solvent conditions did not yield a collagen fragment below 40 000 daltons after pepsin treatment. It was clearly shown that both CGP and GP140 yield type VI collagen fragments in the above-cited reports. Since this report demonstrates that the Mr 30 000 collagen fragment is only released by pepsin treatment of nondenaturing solvent treated periodontal ligament and that only very small peptides are found in denaturing solvent treated tissue after pepsin digestion, it is concluded that the newly isolated Mr 30 000 collagen fragment reported here is not derived from type VI collagen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of low molecular weight actin-binding proteins from porcine brain

Three new actin-binding proteins having molecular weights of 26,000, 21,000, and 19,000 were isolated from porcine brain by DNase I affinity column chromatography. These proteins were released from the DNase I column by elution with a solution of high ionic strength. They were further purified by column chromatographies using hydroxyapatite, phosphocellulose, and Sephadex G-75. All of these actin-binding proteins behaved as monomeric particles in the gel filtration chromatography. After elution of the three actin-binding proteins, actin and profilin were recovered from the DNase I column with 2 M urea solution. The eluted was further purified by a cycle of polymerization and depolymerization and finally by gel filtration. Little difference in polymerizability was detected between the purified brain actin and muscle actin. After sedimentation of the polymerized brain actin, profilin was purified by DEAE-cellulose and gel filtration column chromatographies. In the assay of the action of these actin-binding proteins, the 26K protein was found to cause a large decrease in the rate of actin polymerization, while showing little effect on the extent of polymerization. The 21K protein decreased the steady-state viscosity of actin solution in a concentration-dependent manner irrespective of whether it was added before or after actin polymerization. It reacted with actin at a 1:1 molar ratio.     

Synthesis of immunopoietins--new biologically active low molecular weight fragments of immunoglobulins G, M, E and A

Low-molecular fragments of immunoglobulins IgG-(245-349) (Glu-Pro-Gln-Val-Tyr), IgM-(451-455) (Arg-Pro-Asp-Val-Tyr), IgA-(347-351) (Arg-Pro-Glu-Val-His), and IgE-(430-435) (Ala-Ala-Pro-Glu-Val-Tyr), potentially active immunoregulators of a novel type, have been synthesised by classical methods of peptide chemistry. This group of compounds, which in biological effects are similar to thymopoietin, was given the name of immunopoietins.     

Separation of low molecular weight humic acids with Sephadex G25

Summary A method is pressented using Sephadex G25 to separate the smallest molecules from a humic acid sample. This procedure can also be used to select a certain molecular range.     

Renal reabsorption of low molecular weight proteins in adult male rats: alpha 2u-globulin

Urinary proteins are reabsorbed by the renal tubule cells by two processes, the first for high molecular weight (HMW) and the second for low molecular weight proteins (LMW). The purpose of this report is to establish that alpha 2u-globulin, the sex-dependent, major urinary protein of the adult male rat, is reabsorbed in the kidneys by the general mechanism for LMW proteins. Parameters such as clearance rates were determined to show that alpha 2u is reabsorbed by a process comparable to that for lysozyme. The aminoglycoside, gentamicin, was observed to inhibit the reabsorption of alpha 2u in a dose-dependent fashion. It increased the alpha 2u excretion rate from 4.2 to 13.5 micrograms/min; the clearance was increased from a normal of 0.33 to 0.91 ml/min. The excretion rate for alpha 2u was also increased by the injection of lysozyme from a normal of 7.4 to 18.1 micrograms/min. The effect of lysozyme was dose-dependent and reversible. Although gentamicin and lysozyme each increased the excretion of alpha 2u, they had no effect on albumin. Both were equally effective as inhibitors of alpha 2u reabsorption and were 80% as effective as sodium maleate. It is suggested that alpha 2u is reabsorbed by a mechanism which is shared with other LMW proteins. Furthermore, this process is independent of the one which serves to translocate HMW proteins such as albumin.     

A low molecular weight artificial RNA of unique size with multiple probe target regions

Artificial RNAs (aRNAs) containing novel sequence segments embedded in a deletion mutant of Vibrio proteolyticus 5S rRNA have previously been shown to be expressed from a plasmid borne growth rate regulated promoter in E. coli. These aRNAs accumulate to high levels and their detection is a promising tool for studies in molecular microbial ecology and in environmental monitoring. Herein a new construct is described which illustrates the versatility of detection that is possible with aRNAs. This 3xPen aRNA construct carries a 72 nucleotide insert with three copies of a unique 17 base probe target sequence. This aRNA is 160 nucleotides in length and again accumulates to high levels in the E. coli cytoplasm without incorporating into ribosomes. The 3xPen aRNA illustrates two improvements in detection. First, by appropriate selection of insert size, we obtained an aRNA which provides a unique and hence, easily quantifiable peak, on a high resolution gel profile of low molecular weight RNAs. Second, the existence of multiple probe targets results in a nearly commensurate increase in signal when detection is by hybridization. These aRNAs are naturally amplified and carry sequence segments that are not found in known rRNA sequences. It thus may be possible to detect them directly. An experimental step involving RT-PCR or PCR amplification of the gene could therefore be avoided.     

Synthesis and antimicrobial evaluation of cationic low molecular weight amphipathic 1,2,3-triazoles

A library of 28 small cationic 1,4-substituted 1,2,3-triazoles was prepared for studies of antimicrobial activity. The structures addressed the pharmacophore model of small antimicrobial peptides and an amphipathic motif found in marine antimicrobials. Eight compounds showed promising antimicrobial activity, of which the most potent compound 10b displayed minimum inhibitory concentrations of 4–8 μg/mL against Streptococcus agalacticae, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis. The simple syntheses and low degree of functionalization make these 1,4-substituted 1,2,3-triazoles interesting for further optimizations.     

Localization of low molecular weight GTP binding proteins to exocytic and endocytic compartments

A set of 11 clones encoding putative GTP binding proteins highly homologous to the yeast YPT1/SEC4 gene products have been isolated from an MDCK cell cDNA library. We localized three of the corresponding proteins in mammalian cells by using affinity-purified antibodies in immunofluorescence and immunoelectron microscopy studies. One, the MDCK homolog of rab2, is associated with a structure having the characteristics of an intermediate compartment between the endoplasmic reticulum and the Golgi apparatus. The second, rab5, is located at the cytoplasmic surface of the plasma membrane and on early endosomes, while the third, rab7, is found on late endosomes. These findings provide evidence that members of the YPT1/SEC4 subfamily of GTP binding proteins are localized to specific exocytic and endocytic subcompartments in mammalian cells.     

Purification of low molecular weight copper proteins from copper loaded liver.

Purification of low molecular weight copper binding proteins from the livers of copper loaded male rats was achieved by sequential ultracentrifugation (186,000g, 2h), ultrafiltration (Amicon PM 30), gel filtration (Sephadex G-75) and anion exchange chromatography (DEAE - Biogel A) of soluble tissue extracts. The three major copper-associated polypeptides obtained which had molecular weights of about 7000, 9,000, and 12,000 daltons contained approximately 2.5g atoms of copper per mole. Amino acid analyses indicated a similarity between these proteins and the copper protein ‘L-6D’ isolated earlier from livers of Wilson's disease patients and distinguished them from metallothioneins which have been isolated from animals administered other trace metal ions.     

Development-dependent expression of low molecular weight GTP-binding proteins in embryonic chicken brain

Expression of low molecular weight GTP-binding proteins in particulate and soluble fractions of embryonic chicken brain was analysed by SDS-PAGE and incubation of blotted proteins with [alpha-32P]GTP. At least seven GTP-binding proteins with apparent molecular weights between 21 and 29 kDa were demonstrated by this technique in membranes and microsomal fractions, whereas only four species were present in the cytosol. Levels of several small GTP-binding proteins were developmentally regulated in membrane and microsomal fractions, but not in the cytosol of embryonic chicken brain. Major GTP-binding proteins G28 and G26 were strongly increased in microsomal but not in membrane fractions between E6 and hatched chicken brain, whereas the minor protein G24 decreased in both membrane and microsomal fractions over this time. The differential expression of low molecular weight GTP-binding proteins in embryonic chicken brain suggests important roles for these proteins in brain development.     

Synthesis of high molecular weight DNA strands during S phase

The organization of the mammalian S phase was studied in synchronized mouse embryo cells in terms of the spatial relationship between replication units whose synthesis is initiated at different times in S phase and the rate of assimilation of replication units into high molecular weight DNA strands.The formation of high molecular weight nascent DNA strands several replication units in length was analyzed by velocity sedimentation in alkaline sucrose gradients and by isopycnic centrifugation in alkaline Cs₂SO₄/CsCl gradients. Differential labeling with an isotopic and a density label shows that replication units synthesized at different stages of the S phase are not found within the same high molecular weight polynucleotide strand. It is thus concluded that replication units duplicated at different stages of the S phase are spatially organized in clusters along the mammalian genome.The rate of formation of high molecular weight nascent DNA strands is at least 4 to 8 times slower than that predicted from the spatial organization of replication units and the rate of chain growth within replication units. It is concluded that the process of joining of the completed nascent strands of adjacent replication units plays a major role in the rate of completion of high molecular weight strands.