Limited proteolysis of some egg surface components is an early event following fertilization of the sea urchin, Strongylocentrotus purpuratus.

The surface proteins of eggs from Stronglocentrotus purpuratus were labeled with ¹²⁵I by lactoperoxidase-catalyzed iodination. The eggs were examined after solubilization and disaggregation in sodium dodecyl sulphate (SDS) by electrophoresis on SDS-polyacrylamide slab-gels. Seventy-five percent of the label was found in material with a molecular weight greater than 130,000. About 5% of the radioactivity was excluded from the gels. Upon fertilization, embryos show a redistribution of the radioactively labeled species. There is a decrease in the amount of very high molecular weight material but an increase (35–40%) in material excluded from the gel. In addition, new radioactive bands of lower molecular weight are found. This change of distribution in the radioactive bands is blocked by inclusion of soybean trypsin inhibitor either before or immediately after fertilization, which completely inhibits the cortical granule protease. The disappearance of high molecular weight components is prevented by treatment of the eggs with procaine during fertilization, although the appearance of low molecular weight bands (approximately 20,000 and 30,000) is not completely blocked by procaine treatment. Parthenogenic activation of eggs by butyric acid or partial metabolic activation by ammonia each leads to changes in the egg surface proteins which are similar but not identical to those seen after fertilization. The data suggest that the labeling occurs on the vitelline membrane, plasma membrane and jelly layer. The possible significance of limited proteolysis in fertilization is discussed.     

Depolymerization of lignosulfonates by submerged cultures of the basidiomycete Irpex consors and cloning of a putative versatile peroxidase

Lignosulfonates are abundantly available byproducts of the paper and pulping industry, and they therefore represent a promising feedstock for new sustainable processes. For industrial applications of lignosulfonates, their molecular weight distribution is a critical factor. In order to decrease the average molecular weight of lignosulfonates, Seventeen basidiomycetes were screened for their capability to depolymerize lignosulfonates from spent sulfite liquor (SSL) in surface and liquid cultures. Five basidiomycetes polymerized the lignosulfonates under the selected conditions. Only Irpex consors was found to efficiently degrade calcium lignosulfonates when SSL (0.5%, w/w) was used as the sole carbon and nitrogen source. The average molecular weight of the lignosulfonates was reduced from ∼26 to ∼4 kDa as determined by size exclusion chromatography (SEC) within two weeks. Various extracellular enzyme activities of I. consors were determined over the culture period. High peroxidase activities were correlating with a high degradation rate and the culture was harvested at the day of highest peroxidase activity. A putative versatile peroxidase was isolated by fast protein liquid chromatography (FPLC) and its encoding cDNA was cloned.     

Biochemical isolation and physiological identification of the egg- laying hormone in Aplysia californica

It has been determined that the bag cells of Aplysia californica produce two polypeptide species that comigrate on electrophoretic gels containing sodium dodecyl sulfate. By this separation procedure both species can be assigned a molecular weight of approximately 6,000. One of these molecules has an Rf of 0.65 on alkaline discontinuous electrophoresis gels, an isoelectric point at pH 4.8, a gel filtration molecular weight of approximately 12,000, and has no known biological function. The other does not enter alkaline disk gels, has an isoelectric point at approximately pH 9.3, shows a gel filtration molecular weight consistent with that determined by SDS gel electrophoresis, and is the egg-laying hormone.     

Exploitation of hormone-induced conformational changes to label selectively a component of rat liver plasma membranes.

The kinetics for inactivation of rat liver plasma membrane adenylate cyclase by iodoacetic acid and iodoacetamide has been measured in the presence and absence of glucagon. Glucagon stimulated the rate of iodoacetic acid inhibition by a factor 9f 2.3-fold and iodoacetamide inhibition by 10-fold. These results suggest that interaction of glucagon with its receptor in the membrane resulted in conformational changes which increased either the exposure or nucleophilicity of one or more sulfhydryl groups crucial for adenylate cyclase activity. Membranes were treated with radioactively labeled iodoacetamide or iodoacetic acid in the presence or absence of glucagon and run on 5 and 7.5% sodium dodecylsulfate polyacrylamide gels. These labeling experiments revealed that two membrane components were more extensively labeled in the presence of glucagon. The first component had an apparent molecular weight of 240,000 on sodium dodecyl sulfate gels and stained positive with Coomassie blue and periodate Schiff reagent. This polypeptide accounted for approximately 1.3% of the total membrane protein. The second component had an apparent molecular weight less than 10,000 and could not be correlated directly with a well defined protein band on sodium dodecyl sulfate polyacrylamide gels. The enhancement in labeling of the 240,000 molecular weight component seen in the presence of glucagon agreed very well with that predicted from the kinetics for inhibition of adenylate cyclase activity in the presence and absence of glucagon. This correlation suggests that the component selectively labeled by this technique may be an integral component of the adenylate cyclase system and that hormone-induced conformational changes may be used to selectively label components of the adenylate cyclase system in mammalian membranes.     

Characterization of enzymatic degradation products of carboxymethyl cellulose by gel chromatography

In order to investigate the molecular weight distribution of depolymerization products obtained by enzymatic degradation of carboxymethyl cellulose (CMC), a high resolution size exclusion chromatographic (SEC) system was developed.The SEC system using Fractogel® TSK-HW and an eluent containing sodium sulfate and sodium acetate enables an effective separation of the anionic cleavage products to be carried out. The experimental set-up was equipped with a sensitive detection system based on the post-column reaction of carbohydrates with orcinol.The elution patterns of enzymatic depolymerization products obtained from CMC with different degrees of substitution make it feasible to infer parts of the sequence and the distribution of carboxymethyl groups.     

Protein Components of the Purified Sodium Channel from Rat Skeletal Muscle Sarcolemma

Abstract: Sensitive detection systems have been used to study the protein components of the sodium channel purified from rat skeletal muscle sarcolemma. This functional, purified sodium channel contains at least three subunits on 7–20% gradient sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis: a large glycoprotein which migrates anomalously in the high-molecular-weight range, a 45,000 molecular weight polypeptide, and a third protein often seen as a doublet at 38,000. The large glycoprotein runs as a diffuse band and stains very poorly with Coomassie blue, but is adequately visualized with silver staining or iodination followed by autoradiography. This glycoprotein exhibits anomalous electrophoretic behavior in SDS-polyacrylamide gels. The apparent molecular weight of the center of the band varies from ～230,000 on 13% acrylamide gels to ～130,000 on 5% gels; on 7–20% gradient gels a value of 160,000 is found. Plots of relative migration versus gel concentration suggest an unusually high apparent free solution mobility. Lectin binding to purified channel peptides separated by gel electrophoresis indicates that the large glycoprotein is the only subunit that binds either concanavalin A or wheat germ agglutinin, and this component has high binding capacity for both lectins. The smaller channel components run consistently at 45,000 and 38,000 molecular weight in a variety of gel systems and do not appear to be glycosylated.     

Utilization and polymerization of lignosulfonates by wood-rotting fungi

The susceptibility of lignosulfonates to the action of lignin-degrading wood-rotting fungi was studied by submitting commercial lignosulfonate (Peritan Na) and fractions of calcium lignosulfonate of different molecular weights to the action of selected white rot fungi. As shown by gel filtration chromatography and determinations according to the nitroso method, lignosulfonates, even in conditions which did not support fungal growth, underwent strong polymerization when brought in contact with typical, extracellular polyphenol oxidase-producing white-rot fungi. Owing to the polymerization, nitroso determinations showed a seeming decrease of lignosulfonate. Polyporus dichrous, an “atypical” white-rot fungus which does not produce extracellular polyphenol oxidase and hence does not cause polymerization of lignosulfonates, was found to degrade 11% of the lignosulfonate available in a solid malt extract medium during 19 days. Addition of lignosulfonate to a rich synthetic liquid growth medium increased the mycelial yield of several white-rot fungi. Trametes versicolor was able to grow on a calcium lignosulfonate fraction with molecular weight 1350 which served as sole source of carbon and energy, but not on fractions of higher molecular weight. The utilization/polymerization of lignosulfonates was shown to depend on concentration and on the presence of additional utilizable sources of carbon.     

Isolation ofn-ethylmaleimide-labelled phlorizin-sensitived-glucose binding protein of brush border membrane from rat kidney cortex

A glucose receptor with high affinity for phlorizin from isolated brush border of rat kidney was labelled specifically withN-[¹⁴C]ethylmaleimide and then extracted from the membranes.After the solubilization of the brush borders with sodium dodecyl sulphate theN-[¹⁴C]ethylmaleimide-labelled receptor protein was isolated and was found to have a molecular weight of approximately 30 000 as determined by sodium dodecyl sulphate-polyacrylamide gel disc electrophoresis. The receptor protein eluted from the sodium dodecyl sulphate-containing gels migrates as a single band on sodium dodecyl sulphate-free polyacrylamide gels.The receptor protein can also be released from the brush borders with low concentrations of sodium deoxycholate. Under these conditions the molecular weight of theN-[¹⁴C]ethylmaleimide-labelled receptor protein is approximately 60 000 in contrast to the protein component solubilized with sodium dodecyl sulphate. Since this detergent is known to dissociate the brush border membrane into its protein components, our results suggest that the phlorizin- sensitive glucose receptor protein has a molecular weight of about 30 000.     

Similarity in the Size and Number of Ribosomal Proteins from Different Prokaryotes

The ribosomal proteins from nine species of prokaryotes have been compared by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The stained gels were scanned spectrophotometrically, the weight and number average molecular weights were calculated, and the detailed distribution of the proteins as a function of molecular weight was determined. By all of these criteria, the ribosomal proteins from all the species closely resembled each other, despite differences in the pattern of protein bands by conventional disc-gel electrophoresis. Therefore, it is suggested that the structural requirements for the assembly of ribosomal subunits have imposed limitations on the evolution of the ribosomal proteins and that their size has been highly conserved.     

Activity-dependent phosphorylation of SNAP-25 in hippocampal organotypic cultures

Synaptosomal-associated protein of 25 kDa (SNAP-25) is thought to play a key role in vesicle exocytosis and in the control of transmitter release. However, the precise mechanisms of action as well as the regulation of SNAP-25 remain unclear. Here we show by immunoprecipitation that activation of protein kinase C (PKC) by phorbol esters results in an increase in SNAP-25 phosphorylation. In addition, immunochemical analysis of two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels shows that SNAP-25 focuses as three or four distinct spots in the expected range of molecular weight and isoelectric point. Changing the phosphorylation level of the protein by incubating the slices in the presence of either a PKC agonist (phorbol 12,13-dibutyrate) or antagonist (chelerythrine) modified the distribution of SNAP-25 among these spots. Phorbol 12,13-dibutyrate increased the intensity of the spots with higher molecular weight and lower isoelectric point, whereas chelerythrine produced the opposite effect. This effect was specific for regulators of PKC, as agonists of other kinases did not produce similar changes. Induction of long-term potentiation, a property involved in learning mechanisms, and production of seizures with a GABA(A) receptor antagonist also increased the intensity of the spots with higher molecular weight and lower isoelectric point. This effect was prevented by the PKC inhibitor chelerythrine. We conclude that SNAP-25 can be phosphorylated in situ by PKC in an activity-dependent manner.     

Molecular Properties of the Growth-Associated Protein GAP-43 (B-50)

The protein that has been identified in different contexts as growth-associated protein (GAP)-43, GAP-48, protein 4, B-50, F-1 gamma 5, and pp46, has been implicated in neural development, axonal regeneration, and the modulation of synaptic function. The present study investigated various properties of this protein (designated here as GAP/B-50), including its correct molecular weight and possible polymeric structure. GAP/B-50 was purified to greater than 90% homogeneity using an alkaline extraction procedure followed by a two-stage separation on a size-exclusion HPLC column. The equivalence of the purified protein to the B-50 phosphoprotein was confirmed by peptide digests, comigration, immunostaining, and amino acid composition. On a series of sodium dodecyl sulfate-polyacrylamide gels the apparent molecular weight of the protein was seen to vary inversely with the concentration of acrylamide in the gels. Using these data in the method of Ferguson, the molecular weight of GAP/B-50 was calculated to be 32.8 kilodaltons (kD), considerably lower than the previously reported values of 43-67 kD. The low molecular weight of the protein in the presence of detergent was confirmed by density centrifugation. In the absence of detergent, however, the protein was found to be part of a polymeric structure whose retention time by size-exclusion chromatography indicated a size of 124 kD; this property was also confirmed by density centrifugation under nondetergent conditions. These data suggest the possibility that the native form of GAP/B-50 in the presynaptic membrane may be a tetramer of four identical subunits.     

The estimation and comparison of molecular weight of angiotensin I converting enzyme by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis.

The angiotensin I converting enzyme from rat lung was observed to be a glycoprotein containing 8.3% carbohydrate and consisting of a single polypeptide chain with an estimated molecular weight of 139 000 as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis and 150 000 by sucrose density gradient sedimentation analysis. A comparison of the mobility of angiotensin I converting enzyme from rat lung, rabbit lung, and two hog lung sources on sodium dodecyl sulfate-polyacrylamide gels indicates that all four enzymes have very similar molecular weights and subunit structures. Some previously reported molecular weight discrepancies appear to be due to anomalous behavior of the enzyme of gel filtration.     

Changes in plasma membrane glycoproteins of rat spermatozoa during maturation in the epididymis

Glycoproteins on the plasma membrane of testicular and cauda epididymidal spermatozoa have been labeled with galactose oxidase/NaB [3H]4 and sodium metaperiodate/NaB[3H]4, followed by analysis on SDS polyacrylamide gels. The major glycoprotein labeling on testicular spermatozoa has a molecular weight 110,000 whereas on cauda epididymidal spermatozoa greater than 90% of the radio-label is incorporated into proteins of molecular weight 32,000. These 32,000-mol wt X proteins are homologous with proteins of similar molecular weight purified from the epididymal secretion and which have been shown previously to be synthesized in the caput epididymidis under hormonal control. Immunofluorescence revealed that the 32,000-mol wt proteins are present on the flagellum of mature but not immature spermatozoa and that they have a patchy distribution suggesting that they are mobile within the plane of the membrane. The membrane-bound 32,000-mol wt proteins possess hydrophobic domains as revealed by charge-shift electrophoresis and they also label with a lipophilic photoaffinity probe suggesting that they are in contact with the lipid bilayer. The evidence indicates that there is a considerable reorganization of the molecular structure of the plasma membrane of spermatozoa during maturation in the epididymis and that some of the changes are brought about by a direct interaction with epididymal secretory proteins.     

High-performance liquid chromatography of apolipoproteins in serum high-density lipoproteins

A simple and rapid method for apolipoprotein analysis in serum high-density lipoproteins (HDL) has been developed using high-performance liquid chromatography (HPLC) with sodium phosphate buffer (pH 7.0) containing 0.1% sodium dodecyl sulphate (SDS) as eluent. In contrast to the use of urea solution as an eluent, apolipoproteins can be analysed by applying an incubation mixure of HDL and the eluent buffer. A TSK-GEL column of G3000SW was found to be more profitable than G2000SW or G4000SW for analysis of HDL apolipoproteins. Elution patterns monitored by absorbance at 280 nm using a G3000SW column can give precise quantitative as well as qualitative information about apolipoproteins of molecular weight between 10⁴ and 10⁵. HPLC patterns of HDL apolipoproteins were compared between individual human subjects with various diseases. Elution profiles for lipid components in an incubation mixture were also examined.     

The molecular weight of J chains derived from human immunoglobulin M

J chain was isolated from sulphonated human immunoglobulin M molecules by electrophoresis on polyacrylamide gels. When determined by electrophoresis in sodium dodecyl sulphate-polyacrylamide gels, the molecular weight of the protein was about 27000. After suspension in 5m-guanidine hydrochloride solution for 21 days, two groups of three bands appeared on the gels. Most of the protein dissociated to components of molecular weight 15000. The molecular weight of purified J chain was also determined by ultracentrifugation. In borate-saline solution the average weight-average molecular weight was about 29000. The molecular weight slowly decreased upon prolonged exposure to guanidine hydrochloride, and after 14 days the minimum molecular weight was about 15000. Some association between chains still existed. These data suggest that J chain derived from the paraprotein exists in borate-saline solution as dimers held by strong non-covalent forces.     

Chemical investigations on pig kidney aminoacylase.

1. Preparations of purified pig kidney aminoacylase (N-Acylamino-acid amidohydrolase, EC 3.5.1.14) were obtained by Sephadex and DEAE-cellulose chromatography in homogeneous form as judged by polyacrylamide gel electrophoresis and immunoelectrophoresis. 2. The apparent molecular weight of the enzyme, determined by gel filtration, was about 86 000. After treatment with mercaptoethanol, performic acid or sodium dodecyl sulphate a band with an apparent molecular weight of approximately 43 000 was observed in polyacrylamide gels containing sodium dodecyl sulphate. Thus pig kidney aminoacylase seems to be composed of two subunits. 3. The amino acid composition of the enzyme was determined. Aminoacylase contains 772 amino acids, which corresponds to a molecular weight of 85 500. 12 tryptophan and 12 half-cystine residues were found. 4. Each subunit of the enzyme contains two -SH groups of different reactivity and two disulfide bonds one of which is easily cleaved by -SH compounds, the second only by performic acid oxidation. 5. Chemical modification of two -SH groups abolishes the catalytic activity of aminoacylase. Cleavage of two disulfide bonds also inactivates the enzyme. It is suggested that the enzyme has two active sites each containing an essential -SH group and disulfide bond. One active site is assumed to be part of each subunit.     

Size Distribution of Dispersing Units in Corn Amylose

As the first step to reveal the size distribution of dispersing units in amylose, an amylose sample from corn starch was subjected to gel-filtration chromatography on columns of Sephadex G 200 and Sepharoses 6 B, 4 B and 2 B under protection of the sample from retro-gradation by the use of thiocyanate in the solvent system in the chromatography,

A considerable amount of dispersing units with unexpectedly large size was detected in the amylose sample as a. fraction which was excluded from gels of Sepharoses, though the size distribution was considered to be rather continuous covering the units with smaller size of the regular amylose in the sample. The excluded fraction involved an appreciable amount of aggregates of amylose but no usual amylopectin. Nevertheless, the fraction involved some α-1,6 glucosidic linkages susceptible to isoamylase. The digest of the fraction by the enzyme gave a product which showed size distribution similar to that of the regular size of amylose in the original sample. Both the digested product and the regular amylose had much larger size in molecular weight than the digest of amylopectin by the same enzyme.

The results indicate that the corn amylose sample is a mixture of the units with regular size amylose and those with very large one, the latter having various numbers of branches with the size of regular amylose. Thus, it is considered that the size of dispersing units in the corn amylose sample is characterized as a pattern of such continuous distribution ranging from few hundred thousand up to more than several million in terms of molecular weight.     

High resolution two-dimensional electrophoresis of basic as well as acidic proteins.

A previously described two-dimensional electrophoresis procedure (O'Farrell, 1975) combined isoelectric focusing and sodium dodecylsulfate slab gel electrophoresis to give high resolution of proteins with isoelectric points in the range of pH 4–7. This paper describes an alternate procedure for the first dimension which, unlike isoelectric focusing, resolves basic as well as acidic proteins. This method, referred to as nonequilibrium pH gradient electrophoresis (NEPHGE), involves a short time of electrophoresis toward the cathode and separates most proteins according to their isoelectric points. Ampholines of different pH ranges are used to optimize separation of proteins with different isoelectric points. The method is applied to the resolution of basic proteins with pH 7–10 Ampholines, and to the resolution of total cellular proteins with pH 3.5–10 Ampholines. Histones and ribosomal proteins can be readily resolved even though most have isoelectric points beyond the maximum pH attained in these gels. The separation obtained by NEPHGE with pH 3.5–10 Ampholines was compared to that obtained when isoelectric focusing was used in the first dimension. The protein spot size and resolution are similar (each method resolving more than 1000 proteins), but there is less resolution of acidic proteins in this NEPHGE gel due to compression of the pattern. On the other hand, NEPHGE gels extend the range of analysis to include the 15–30% of the proteins which are excluded from isoelectric focusing gels. The distribution of cell proteins according to isoelectric point and molecular weight for a procaryote (E. coli) was compared to that of a eucaryote (African green monkey kidney); the eucaryotic cell proteins are, on the average, larger and more basic.     

Major high mobility group like proteins of Drosophila melanogaster embryonic nuclei

Nuclei from Drosophila melanogaster embryos contain three major proteins which are extracted by 0.35 M NaCl and by 2% perchloric acid. One of these is histone H1, and we refer to the other two as A63 and A13 in accordance with their molecular weights determined by electrophoresis on sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gels (63,000 and 13,000, respectively). The molecular weight of A13, based on its amino acid composition, is approximately 10,000. The amino acid analyses of A63 and A13 show that both of these proteins have high proportions of acidic and basic amino acid residues, a property characteristic of the high mobility group proteins isolated from vertebrate tissues. While A13 comigrates with histone H2A on NaDodSO4-polyacrylamide gels and with H2B on acid/urea gels, it can be readily resolved from the histones by Triton/acid/urea-Na DodSO4 two-dimensional electrophoresis.     

Effects of pronase and neuraminidase treatment on a myelin-associated glycoprotein in developing brain.

Rats (14 days old) were injected with [14c]fucose and young adult rats with [3H]fucose in order to label the myelin-associated glycoproteins. As previously reported, the major [14C]fucose-labelled glycoprotein in the immature myelin had a higher apparent molecular weight on sodium dodecyl sulphate/polyacrylamide gels that the [3H]fucose-labelled glycoprotein in mature myelin. This predominant doubly labelled glycoprotein component was partially purified by preparative gel electrophoresis and converted to glycopeptides by extensive Pronase digestion. Gel filtration on Sephadex G-50 separated the glycopeptides into several clases, which were designted A,B, C AND D, from high to low molecular weight. The 14C-labelled glycopeptides from immature myeline were enriched in the highest-molecular-weight class A relative to the 3H-labelled glycopeptides from mature myelin. Neuraminidase treatment of the glycoprotein before Pronase digestion greatly decreased the proportion of glycopeptides fractionating in the higher-molecular-weight classes and largely eliminated the developmental differences that were apparent by gel filtration. However, neuraminidase treatment did not decrease the magnitude of the developmental difference revealed by electrophoresing the intact glycoprotein on sodium dodecyl sulphate gels, although it did decrease the apparent molecular weight of the glycoprotein from both the 15-day-old and adult rats by an amount comparable in magnitude to that developmental difference. The results from gel filtration of glycopeptides indicate that there is a higher content of large molecular weight, sialic acid-rich oligosaccharide units in the glycoprotein of immature myelin. However, the higher apparent molecular weight for the glycoprotein from 15-day-old rats on sodium dodcyl sulphate gels is not due primarily to its higher sialic acid content.