Characterization of recombinant and natural forms of the human LIM domain-containing protein FHL2

FHL2 (Four and a Half LIM domain-containing protein 2) is a member of a small family of proteins with four LIM domains and an N-terminal half LIM domain. It is an intracellular protein thought to function as an adaptor in the formation of multi-protein complexes involved in signaling. To obtain human FHL2 in amounts allowing further characterization, we evaluated different expression systems and chose to express FHL2 with a His6 tag in insect cells using the baculovirus system. The recombinant protein was highly expressed and could be purified to >98% homogeneity as judged by SDS-PAGE analysis. Purified recombinant FHL2 was used to generate antibodies allowing detection and immunoprecipitation of FHL2 from human cells. Both recombinant and natural FHL2 were characterized by SDS-PAGE and MALDI-TOF mass spectrometry. The molecular mass of the recombinant His6-tagged protein obtained by mass spectrometry was 36,995Da, in good agreement with the apparent mass of 36kDa in SDS-PAGE and slightly higher than the 35,981Da calculated from the sequence of the construct. The measured molecular mass of natural human FHL2 was 32,742Da and the calculated mass was 32,192Da. However, the apparent molecular mass in SDS-PAGE is 41kDa, indicating that the natural protein has an abnormal electrophoretic mobility. The results show that both the recombinant and the natural proteins are post-translationally modified and indicate that such modifications may lead to an abnormal electrophoretic behavior of natural human FHL2.     

苹果多酚氧化酶的纯化与表征

运用丙酮浸漬干燥、磷酸盐缓冲液提取、低温离心、硫酸铵沉淀、DEAE-Sephadex(A-50)、Sephadex(G-75) 和DEAE-celluse(DE-52)层析等方法从苹果中分离获得一种新的含铜酶蛋白,该酶被命名为多酚氧化酶Ⅱ(polyphenol oxidase Ⅱ, PPOⅡ),纯化倍数是215,纯化收率是23%.PAGE、SDS-PAGE和MALDI-TOF 等技术用于测定所获的酶的纯度和分子量.在PAGE和SDS-PAGE 均显示一条带,表明PPOⅡ只由一个亚基组成,且已达到单一组分(MALDI-TOF的结果更证实了这一点).SDS-PAGE 和 MALDI-TOF 的结果都表明PPO的分子量为 38204 Da.pH值对酶活性和稳定性研究的结果显示,从pH值4.0～7.0随着pH值的增加,酶活性也不断增加;从pH值 7.0～11.0, 酶活性不断降低.PPOⅡ的最适pH值为6.6最适温度为30℃.     

2-Methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency is caused by mutations in the HADH2 gene

2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiency is a novel inborn error of isoleucine degradation. In this article, we report the elucidation of the molecular basis of MHBD deficiency. To this end, we purified the enzyme from bovine liver. MALDI-TOF mass spectrometry analysis revealed that the purified protein was identical to bovine 3-hydroxyacyl-CoA dehydrogenase type II. The human homolog of this bovine enzyme is a short-chain 3-hydroxyacyl-CoA dehydrogenase, also known as the "endoplasmic reticulum-associated amyloid-beta binding protein" (ERAB). This led to the identification of the X-chromosomal gene involved, which previously had been denoted "HADH2." Sequence analysis of the HADH2 gene from patients with MHBD deficiency revealed the presence of two missense mutations (R130C and L122V). Heterologous expression of the mutant cDNAs in Escherichia coli showed that both mutations almost completely abolish enzyme activity. This confirms that MHBD deficiency is caused by mutations in the HADH2 gene.     

The 23-kilodalton protein, a substrate of protein kinase C, in bovine neutrophil cytosol is a member of the S100 family.

A bovine neutrophil protein termed p23 because of an apparent molecular mass of 23 kDa in SDS-PAGE is present in large amounts both in a soluble form in the cytosolic fraction of bovine neutrophil homogenates and associated to the cytoskeleton. P23 is accompanied during the first steps of the purification procedure by a smaller size protein termed p7 on the basis of a rate of migration in SDS-PAGE corresponding to a 7-kDa protein [Stasia, M. J., Dianoux, A. C., & Vignais, P. V. (1989) Biochemistry 28, 9659-9667]. The two proteins, p23 and p7, have been purified to homogeneity by an improved procedure consisting of two chromatographic steps. The electrospray mass spectrometry technique applied to p23 and p7 indicated molecular masses close to 17 and 10 kDa, respectively, significantly different from the masses derived by SDS-PAGE. Bovine neutrophil p23 and p7 presented large primary structure homologies with two human proteins, MRP14 and MRP8, which are expressed in large amounts in macrophages under conditions of chronic inflammation. In addition, p23 and p7 cross-reacted with monoclonal antibodies specific of MRP14 and MRP8. Bovine p23 and p7 bound Ca2+, and their amino acid sequences contained two Ca(2+)-binding domains per protein, largely identical to those of human MRP14 and MRP8. Bovine p23 and p7 associated together to form a heterodimeric complex, which largely escaped attack by trypsin, whereas the isolated p23 and p7 components were readily digested. These features are typical of Ca(2+)-binding proteins belonging to the S100 family.(ABSTRACT TRUNCATED AT 250 WORDS)     

MALDI mass sequencing and characterization of filarialglutathione-S-transferase

Glutathione-S-transferase has been detected in the somatic extract and excretory-secretory products of different life stages of Setaria cervi, a bovine filarial parasite. The enzyme was subjected to MALDI-TOF followed by mass spectrometry and the nearest match found was Pleuronectes platessa GST. Molecular mass of the purified enzyme was approximately 26 kDa as determined by SDS-PAGE and MALDI-TOF. Setaria cervi GST exhibited high activity towards 1-chloro-2,4-dinitrobenzene and ethacrynic acid. Kinetic analysis with respect to 1-chloro-2,4-dinitrobenzene and glutathione as substrate revealed a K(m) of 2.22 mM and 0.61 mM, respectively. The activity was inhibited significantly by Cibacron blue and alpha-tocopherol.     

Characterization and kinetics studies of water buffalo (Bubalus bubalis) myoglobin

The colour of buffalo (Bubalus bubalis L.) meat is darker than bovine meat. Since meat colour depends on the concentration of myoglobin (Mb) and its oxidation state, we have determined the main structural and functional properties of buffalo Mb. Buffalo Mb was purified from longissimus dorsi muscles and its molecular mass determined by ESI Q-TOF mass spectrometry. The molecular mass 17,034.50 was 86.20 Da higher than the bovine Mb. This was confirmed by analysing its primary structure, using a combined approach based on Edman degradation and MALDI-TOF mass spectrometry. Comparing the amino acid sequences of both Mbs, we found three amino acid differences out of 153 amino acid residues. One is a conservative substitution (D(bov)141E(buf)), and the other two (A(bov)19T(buf) and A(bov)117D(buf)) are nonconservative. These amino acid substitutions are unlikely to cause structural changes because they are located far from the heme binding pocket, as revealed by the 3D structure of buffalo Mb elaborated by homology modelling. Stability analyses show no difference with the bovine Mb for helix E and only minor differences in the stability values for helices A and G. Moreover, autoxidation rates of purified buffalo and bovine myoglobins at 37 degrees C, pH 7.2, were almost identical, 0.052+/-0.001 h(-1) and 0.054+/-0.002 h(-1), respectively, as were their oxygen-binding Kd values, 3.7+/-0.1 microM and 3.5+/-0.1 microM, respectively. The percent of MetMb values were almost identical. The results presented here suggest that the darker buffalo meat depends on factors other than the oxidation rate of its Mb, as, for example, the Mb content (0.393+/-0.005 g/100 g of tissue) and consequently MetMb, which are almost twice as high as bovine meat (Mb: 0.209+/-0.003 g/100 g of tissue).     

Purification and biochemical characterization of cytosolic glutathione-S-transferase from filarial worms Setaria cervi

The present study reports the purification and characterization of GST from cytosolic fraction of Setaria cervi. GST activity was determined in various subcellular fractions of bovine filarial worms S. cervi (Bubalus bubalis Linn.) and was found to be localized mainly in the cytosolic and microsomal fractions. The soluble enzyme from S. cervi was purified to homogeneity using a combination of salt precipitation, centrifugation, cation exchange and GSH-Sepharose affinity chromatography followed by ultrafiltration. SDS-PAGE analysis revealed a single band and activity staining was also detected on PAGE gels. Gel filtration and MALDI-TOF studies revealed that the native enzyme is a homodimer with a subunit molecular mass of 24.6 kDa. Comparison of kinetic properties of the parasitic and mammalian enzymes revealed significant differences between them. The substrate specificity and inhibitor profile of cytosolic GST from S. cervi appeared to be different from GST from mammalian sources.     

Horse plasma ceruloplasmin molecular weight and subunit analysis

Ceruloplasmin is a blue copper-containing serum glycoprotein with oxidase activity. It as been proposed that the physiological function of ceruloplasmin involves the oxidation of ferrous iron and its incorporation into apotransferrin. There are several reports demonstrating that ceruloplasmin is made up of multiple chains. Ryden has questioned the multichain structure of ceruloplasmin from human, pig, horse and rabbit sera, arguing that the dissociation observed by previous workers could be attributed to cleavage of labile bands in the protein by enzymatic contaminants present in commercial preparations of the protein. By introducing epsilon-aminocaproic acid, a general protease inhibitor, at the beginning of the enzyme preparation, Ryden proposed a single-chain structure for ceruloplasmin. On the contrary the results presented by Freeman and Daniel showed that human ceruloplasmin is a multichain protein. In this paper we report a new purification method for horse ceruloplasmin which furnishes a homogeneous protein preparation in high yield and with good reproducibility. This procedure allowed to determine with greater accuracy the molecular mass of the protein, of 120,000 daltons by gel chromatography and 115,000 daltons by SDS gel electrophoresis. The protein is composed of one unit only and contains 6 copper atoms. Horse ceruloplasmin is a glycoprotein containing about 20% carbohydrate by weight.     

Purification of a plasminogen activator from Streptococcus uberis

Abstract A protein capable of activating bovine, equine and ovine plasminogen, but not that from human or porcine plasma, was purified from culture filtrates of Streptococcus uberis (strain 0140j). Purification was achieved by ammonium sulphate precipitation followed by molecular exclusion chromatography. The elution position of the native molecule was equivalent to a molecular mass of approximately 57 kDa. However, the molecular mass, as determined by SDS-PAGE, was 29 kDa, suggesting the existence of a dimeric structure. Purified immunoglobulin from three out of five monoclonal antibodies raised to this protein inhibited the conversion of bovine plasminogen to plasmin by the purified protein.     

Hemin-induced lysis of rat erythrocytes. Protective action of ceruloplasmin and different serum albumins

Hemin-induced lysis of rat erythrocytes is markedly reduced by ceruloplasmin (human) and serum albumins from different species, the order of effectiveness beings: bovine albumin approximately equal to ceruloplasmin greater than human albumin approximately equal to dog albumin greater than apotransferrin (human). Although the proteins studied had hemin binding capacity, the best protective agents, ceruloplasmin and bovine albumin, did bind hemin less strongly than human and dog albumin. The results suggest the existence of another protective mechanism, possibly involving an interaction between erythrocyte membranes and serum proteins.     

Differential inactivation and separation of homologous and heterologous antiviral activity of human leukocyte interferon by a proteolytic enzyme.

Human leukocyte interferon (HuLeIF) can express its antiviral activity on both human and bovine cells. The rates of inactivation of HuLeIF by α-chymotrypsin, as expressed on human and bovine cells, are not the same: the ability to induce activity on human cells is lost significantly more rapidly than the activity detected on bovine cells; usually a margin of greater than one hundred-fold exists after α-chymotrypsin treatment. HuLeIF, when subjected to analysis on 10% SDS-PAGE, can be separated into two molecular weight species, one having apparent molecular weight of approximately 21,000 daltons, the other 18,000 daltons. A more rapidly migrating form (molecular weight 16,500 daltons) can also be isolated, which is considerably more active on bovine cells than on human cells. α-chymotrypsin-treated samples analyzed by SDS-PAGE show a clear separation of the activities expressed on human and bovine cells. The residual activity detected on human cells is isolated only in the 21,000 component while the activity found on bovine cells is recovered only as the 16,500 dalton species.     

Demonstration by Mass Spectrometry that Purified Native Treponema pallidum Rare Outer Membrane Protein 1 (Tromp1) Has a Cleaved Signal Peptide

Purified native Tromp1 was subjected to mass spectrometric analysis in order to determine conclusively whether this protein possesses a cleaved or uncleaved signal peptide. The molecular masses of Tromp1, three Treponema pallidum lipoproteins, and a bovine serum albumin (BSA) control were determined by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. The molecular masses of all of the T. pallidum lipoproteins and BSA were within 0.7% of their respective calculated masses. The molecular mass of Tromp1 was 31,510 Da, which is consistent with a signal-less form of Tromp1, given a calculated mass of unprocessed Tromp1 of 33, 571 Da, a difference of 2,061 Da (a 6.5% difference). Purified native Tromp1 was also subjected to MALDI-TOF analysis in comparison to recombinant Tromp1 following cyanogen bromide cleavage, which further confirmed the identity of Tromp1 and showed that native Tromp1 was not degraded at the carboxy terminus. These studies confirm that Tromp1 is processed and does not contain an uncleaved signal peptide as previously reported.     

Purification and characterization of hydrosoluble components from the sap of Chinese lacquer tree Rhus vernicifera

Continuous gradient elution chromatography (CGEC) was employed to purify and separate enzymes and polysaccharides from the sap of Rhus vernicifera Chinese lacquer tree. There are three different molecules with laccase enzyme activity. Two are enzymes of each other (L1, and L2), whereas the third (RL) is an entirely separate entity. Two polysaccharides (GP1 and GP2) were also found. The Rhus laccase (RL), and isoenzymes L1 and L2, have peak molecular masses of 109,100, 120,000, 103,000 respectively; each has four copper atoms per molecule, and the pI values were 8.2, 8.6, and 9.1, respectively. The structure of the laccases was studied by Fourier-transform infrared (FT-IR) and Matrix-assisted laser desorption/ionization time-of flight (MALDI-TOF) mass spectrometry. The typical amide I (1646 cm⁻¹) and amide II (1545 cm⁻¹) bands were observed. The results from MALDI-TOF were similar to those from CGEC, but the molecular mass from the MALDI-TOF was significantly different from that obtained from sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).     

Proteome Analysis of Cerebrospinal Fluid in Amyotrophic Lateral Sclerosis (ALS)

Cerebrospinal fluid (CSF) is a promising source of biomarkers in amyotrophic lateral sclerosis (ALS). Using the two-dimensional difference in gel electrophoresis (2-D-DIGE), we compared CSF samples from patients with ALS (n = 14) with those from normal controls (n = 14). Protein spots that showed significant differences between patients and controls were selected for further analysis by MALDI-TOF mass spectrometry. For validation of identified spots western blot analysis and ELISA was performed. We identified 2 proteins that were upregulated and 3 proteins that were down-regulated in CSF in ALS. Of these, two proteins (Zn-alpha-2-glycoprotein and ceruloplasmin precursor protein) have not been reported in CSF of patients with ALS so far. In contrast, several other proteins (transferrin, alpha-1-antitrypsin precursor and beta-2-microglobulin) seem to be unspecifically affected in different neurological diseases and may therefore be of limited value as disease-related biochemical markers in ALS. Further evaluation of the candidate proteins identified here is necessary.     

Study on agglutinating factors from flocculent Saccharomyces cerevisiae strains

The lectin-like theory suggest that yeast flocculation is mediated by an aggregating lectinic factor. In this study we isolated an agglutinating factor, which corresponds to lectin, from whole cells by treating the flocculent wild-type Saccharomyces cerevisiae NCYC 625 strain and its weakly flocculent mutant [rho degrees ] with EDTA and two non-ionic surfactants (Hecameg and HTAC). The dialysed crude extracts obtained in this way agglutinated erythrocytes and this hemagglutination was specifically inhibited by mannose and mannose derivatives. However, SDS-PAGE profiles showed that the three reagents had different effects on the yeast cells. The non-ionic surfactants appeared to be the most efficient, as their extracts possessed the highest specific agglutinating activity. The products released by the wild-type strain presented a higher specific agglutinating activity than those released by the [rho degrees ] mutant. Purification of the agglutinating factor from extracts of both strains by affinity chromatography revealed two active bands of relative mass of 26 and 47 kDa on SDS-PAGE. Mass spectrometry analysis by MALDI-TOF, identified a 26 kDa band as the triose phosphate isomerase (TPI) whereas a 47 kDa band was identical to enolase. Edman degradation showed that the N-terminal sequences of these proteins were similar to TPI and enolase, respectively. The difference in the flocculation behaviour of the two strains is due to changes in the protein composition of the cell wall and in the protein structure involved in cell-cell recognition.     

Coagulation Factor V contains copper ion

Preparations of bovine and human coagulation Factor V were analyzed for copper using both atomic absorption and atomic emission spectroscopy. All preparations of the bovine and human protein were found to contain copper ion at a ratio of 1 copper ion bound per mol (Mr = 330,000) of Factor V. As a result of copper binding and sequence homology between ceruloplasmin and Factor V, bovine Factor V and thrombin-activated Factor V (Va) were assessed with respect to their visible and near ultraviolet absorption spectra and to their ability to oxidize N,N-dimethyl-p-phenylenediamine (a substrate for ceruloplasmin). Factor V and Factor Va exhibited absorption spectra with no maxima at either 310 or 610 nm, indicating that the copper is not bound in a site analogous to Type I or Type III copper sites in ceruloplasmin. Further, Factor V and Factor Va are not capable of serving as catalysts for the oxidation of N,N-dimethyl-p-phenylenediamine under solution conditions that are optimum for ceruloplasmin oxidase activity. These data suggest that the copper ion bound to Factor V may be functionally and structurally distinct from the Type I and Type III copper ion bound to ceruloplasmin.     

The size and shape of human and bovine antithrombin III.

Human and bovine antithrombin, purified by affinity chromatography on heparin-agarose, have been characterized with regard to chemical composition, size, shape and conformation. Both preparations were found to contain several active components of identical or similar size but different electrical charge. Amino acids and carbohydrate analyses revealed striking similarities between human and bovine antithrombin, while immunological analyses failed to demonstrate any cross-reactivity. The molecular weights were determined by sedimentation equilibrium to be 58 000 for human and 56 000 for bovine antithrombin. The small molecular weight difference suggested by these values was verified by several empirical methods of molecular weight estimation. Hydrodynamic measurements indicated that the two proteins have similar molecular shapes, both of which are slightly more extended that that of typical globular proteins. The internal folding of the two polypeptide chains is also similar, as evidenced by the identity of the far-ultraviolet circular dichroism spectra. Specifically, these analyses suggested a low alpha-helix content of both proteins. In conclusion, the marked structural similarity of human and bovine antithrombin indicates that the two proteins may also exhibit extensive functional similarities in the binding of heparin and the inhibition of various coagulation factors.     

Horse Plasma Ceruloplasmin Molecular Weight and Subunit Analysis

Ceruloplasmin is a blue copper-containing serum glycoprotein with oxidase activity. It as been proposed that the physiological function of ceruloplasmin involves the oxidation of ferrous iron and its incorporation into apotransferrin (1). There are several reports demonstrating that ceruloplasmin is made up of multiple chains (2-3-4-5-6-7). Ryden (8) has questioned the multichain structure of ceruloplasmin from human, pig, horse and rabbit sera, arguing that the dissociation observed by previous workers could be attributed to cleavage of labile bands in the protein by enzymatic contaminants present in commercial preparations of the protein. By introducing aminocaproic acid, a general protease inhibitor, at the beginning of the enzyme preparation, Ryden proposed a single-chain structure for ceruloplasmin. On the contrary the results presented by Freeman and Daniel (9) showed that human ceruloplasmin is a multichain protein.

In this paper we report a new purification method for horse ceruloplasmin which furnishes a homogeneous protein preparation in high yield and with good reproducibility.

This procedure allowed to determine with greater accuracy the molecular mass of the protein, of 120000 dal-tons by gel cromatography and 115000 daltons by SDS gel electrophoresis. The protein is composed of one unit only and contains 6 copper atoms. Horse cerulopla-smin is a glycoprotein containing about 20% carbohydrate by weight.     

A simple search of TM segments in polytopic membrane protein using matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Using both high performance liquid chromatography (HPLC) and amino acid sequencing (AAS), we previously analyzed band 3 TM peptide-segments that make up the transmembrane protein structure. However, the HPLC/AAS combination method was highly time-consuming. Matrix-Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry is used to obtain accurate molecular weight information for proteins/peptides simply and sensitively. We applied the MALDI-TOF mass spectrometry technique to search for TM segments in membrane proteins. In combination with trypsin cleavages after alkali treatments (pH12 or 13) and sample preparation using organic solvents for MALDI-TOF mass spectrometry, we determined the TM segments of band 3 and glycophorin A in erythrocyte membrane. The method can be applied to other polytopic membrane proteins in erythrocyte membrane.