Complete amino acid sequence of chitinase-A from leaves of pokeweed (Phytolacca americana).

The complete amino acid sequence of pokeweed leaf chitinase-A was determined. First all 11 tryptic peptides from the reduced and S-carboxymethylated form of the enzyme were sequenced. Then the same form of the enzyme was cleaved with cyanogen bromide, giving three fragments. The fragments were digested with chymotrypsin or Staphylococcus aureus V8 protease. Last, the 11 tryptic peptides were put in order. Of seven cysteine residues, six were linked by disulfide bonds (between Cys25 and Cys74, Cys89 and Cys98, and Cys195 and Cys208); Cys176 was free. The enzyme consisted of 208 amino acid residues and had a molecular weight of 22,391. It consisted of only one polypeptide chain without a chitin-binding domain. The length of the chain was almost the same as that of the catalytic domains of class IL chitinases. These findings suggested that this enzyme is a new kind of class IIL chitinase, although its sequence resembles that of catalytic domains of class IL chitinases more than that of the class IIL chitinases reported so far. Discussion on the involvement of specific tryptophan residue in the active site of PLC-A is also given based on the sequence similarity with rye seed chitinase-c.

Primary structure of 6.5k-arginine/glutamate-rich polypeptide from the seeds of sponge gourd (Luffa cylindrica).

The amino acid sequence of 6.5k-arginine/glutamate rich polypeptide (6.5k-AGRP) from the seeds of sponge gourd (Luffa cylindrica) has been determined. The 6.5k-AGRP consists of a 47-residue polypeptide chain containing two disulfide bonds, and a molecular mass calculated to be 5695 Da, which fully coincides with a value of [M+H]+ = m/zeta 5693.39 obtained by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The mass spectrometric evidence indicated that 6.5k-AGRP is also present partially truncated at the C-terminus. In our preparations, approximately half of the polypeptide molecules have the C-terminal sequence Arg-Arg-Glu-Val-Asp; the other half lack Val-Asp and end with the glutamic acid, making a total of 45 residues in the polypeptide chain. The two disulfide bonds connect Cys12 to Cys33 and Cys16 to Cys29. Comparison of the amino acid sequence of 6.5k-AGRP with those of the other known proteins included in the PIR protein sequence database showed that it is related to the amino acid sequence of the N-terminal region encoded by the first exon of the cocoa (Theobroma cacao) and cotton seeds vicilin genes, sharing a characteristic two Cys-Xaa-Xaa-Xaa-Cys motif.

Actions of pokeweed antiviral protein on virus-infected protoplasts.

Pokeweed antiviral protein (PAP) belongs to a group of ribosome-inactivating proteins (RIPs) that inactivate ribosomes by depurinating rRNA at a specific site. To study the mechanism for the antiviral activity of PAP, the actions of PAP on TMV-infected and uninfected tobacco protoplasts were investigated. The addition of 0.33 microM PAP to TMV-inoculated protoplasts caused a complete inhibition of TMV production. The same concentration of PAP was found to inhibit protein synthesis in the virus-infected protoplasts and to kill the cells, but it had no effect on the uninfected protoplasts. The concentration dependence of protein synthesis-inhibition by PAP was related to that of inhibition of viral multiplication. Furthermore, two other RIPs (ricin A-chain and luffin-a), which showed 240 and 430-fold less activity on tobacco ribosomes than PAP in a cell-free system, did not inhibit viral multiplication even at a concentration of 3.3 microM. The analysis of RNAs from the virus-infected and PAP-treated protoplasts demonstrated that 25S rRNA was depurinated by PAP in the infected cells. These results suggest that PAP, which is normally unable to penetrate the plasma membrane of uninfected protoplasts, gains entrance to the cytosol of infected cells and prevents viral multiplication by inactivating ribosomes.

The amino acid sequence of mitogenic lectin-B from the roots of pokeweed (Phytolacca americana).

The complete amino acid sequence of pokeweed lectin-B (PL-B) has been analyzed by first sequencing seven lysylendopeptidase peptides derived from the reduced and S-pyridylethylated PL-B and then connecting them by analyzing the arginylendopeptidase peptides from the reduced and S-carboxymethylated PL-B. PL-B consists of 295 amino acid residues and two oligosaccharides linked to Asn96 and Asn139, and has a molecular mass of 34,493 Da. PL-B is composed of seven repetitive chitin-binding domains having 48-79% sequence homology with each other. Twelve amino acid residues including eight cysteine residues in these domains are absolutely conserved in all other chitin-binding domains of plant lectins and class I chitinases. Also, it was strongly suggested that the extremely high hemagglutinating and mitogenic activities of PL-B may be ascribed to its seven-domain structure.

Isolation and molecular characterization of four arginine/glutamate rich polypeptides from the seeds of sponge gourd (Luffa cylindrica).

Four arginine/glutamate rich polypeptides referred to as 5 k-, 6.5 k-, 12.5 k-, and 14 k-AGRPs were purified to homogeneity by gel filtration on Sephadex G-75 followed by CM-cellulose, butyl-Toyopearl 650 M, and reverse-phase HPLC from the seed of sponge gourd (Luffa cylindrica). Tricine SDS-PAGE indicated that 5 k- and 6.5 k-AGRPs are single polypeptides, but 12.5 k- and 14 k-AGRPs consist of two polypeptide chains, which are linked by disulfide bond(s). The N-terminal amino acid sequences of four AGRPs were analyzed by a gas-phase sequencer, and the result indicated that they are distinct molecules. Comparison of the sequences with those of proteins in the protein data base demonstrates that 5 k- and 6.5 k-AGRPs have a significant homology with a basic peptide from pumpkin seeds and with cocoa seed vicilin, respectively, and that 12.5 k- and 14 k-AGRPs are related to 2S seed storage proteins. Furthermore, it was assumed that the four AGRPs might occur in the protein bodies within cells of the seed.

Crystallization and preliminary X-ray studies of two serine proteinase inhibitors, BGIA and BGIT, from the seeds of bitter gourd.

Two serine proteinase inhibitors from seeds of the bitter gourd, BGIA (bitter gourd inhibitor against acidic amino acid-specific proteinase of Streptomyces griseus) and BGIT (bitter gourd trypsin inhibitor), were crystallized for X-ray structure determination. Crystals of BGIA belong to the monoclinic space group C2 with cell dimensions of a = 54.0 A, b = 23.7 A, c = 47.9 A, and beta = 105.4 degrees, and diffracted X-ray up to 1.5 A resolution. Crystals of BGIT belong to the triclinic space group P1 with cell dimensions of a = 22.8 A, b = 23.5 A, c = 28.4 A, alpha = 93.1 degrees, beta = 99.6 degrees, and gamma = 101.0 degrees, giving X-ray diffraction of over 1.2 A resolution. Intensity data of BGIA and BGIT crystals were collected using synchrotron radiation up to 1.7 and 1.4 A, respectively.

Amino acid sequence and some properties of lectin-D from the roots of pokeweed (Phytolacca americana).

Two pokeweed lectins, designated PL-D1 and PL-D2, have been isolated from the roots of pokeweed (Phytolacca americana) using chitin affinity column chromatography followed by gel filtration on a Sephacryl S-200 column and fast protein liquid chromatography on a Mono-Q column, and their amino acid sequences have been analyzed. PL-D1 consists of 84 amino acid residues and has a molecular mass of 9317, while PL-D2 has an identical sequence with PL-D1 except lack of the C-terminal Leu-Thr. PL-D is composed of two chitin-binding domains, A and B, with 50% homology with each other. Both PL-Ds did not agglutinate native rabbit erythrocytes, but showed about 0.1% of the agglutinating activity of wheat germ agglutinin toward trypsin-treated erythrocytes. In the presence of beta (1-->4) linked oligomers of N-acetyl-D-glucosamine, which inhibit the hemagglutination, PL-D1 had an ultraviolet-difference spectrum with maxima at 292-294 nm and 284-285 nm, attributed to the red shift of the tryptophan residue, suggesting the location of tryptophan residue(s) at or near saccharide-binding site of PL-D1.

Limited proteolysis and reduction-carboxymethylation of rye seed chitinase-a: role of the chitin-binding domain in its chitinase action.

By a limited proteolysis with thermolysin, rye seed chitinase-a (RSC-a) was separated into a N-terminal cysteine-rich chitin-binding (CB-) domain (48 residues) and a catalytic (Cat-) domain (254 residues). The hydrolytic activity of the isolated Cat-domain toward soluble glycolchitin, was similar to that of RSC-a, but that toward insoluble colloidal chitin was 28% of that of RSC-a. Five disulfide bonds in the CB-domain were reduced with 2-mercaptoethanol (2-ME) in the absence of denaturing agents by an "all-or-none" process, that is, once the disulfide bond between Cys15 and Cys42 in the CB-domain was cleaved, the remaining four disulfide bonds were reduced very easily. The reduced and carboxymethylated RSC-a completely lost the chitin-binding ability, but retained 50% of the hydrolytic activity toward colloidal chitin of RSC-a. From these results, it was shown that RSC-a consists of a CB-domain and a Cat-domain connected by a flexible linker, and it was suggested that the CB-domain increases the hydrolytic action of Cat-domain toward insoluble chitin derivatives by binding to them.

Isolation from alpha-zein of thermolysin peptides with angiotensin I-converting enzyme inhibitory activity.

Urea-denatured alpha-zein was almost completely hydrolyzed into small peptides by digestion with 1/100 (w/w) of thermolysin at 37 degrees C for 3h. The angiotensin I-converting enzyme (ACE) inhibitory activity (IC50) of the thermolysin digest of total alpha-zein was 24.5 micrograms/ml, and most of the peptide fractions from Z19 alpha-zein and total alpha-zein separated by reverse-phase HPLC had more or less ACE inhibitory activity. From these fractions, thirty-six peptides, including 5 dipeptides, 14 tripeptides, 9 tetrapeptides, 5 pentapeptides, and 3 hexapeptides, were purified and their amino acid sequences were determined.

The complete amino acid sequence of lectin-C from the roots of pokeweed (Phytolacca americana).

The complete amino acid sequence of pokeweed lectin-C (PL-C) consisting of 126 residues has been determined. PL-C is an acidic simple protein with molecular mass of 13,747 Da and consists of three cysteine-rich domains with 51-63% homology. PL-C shows homology to chitin-binding proteins such as wheat germ agglutinin, and all eight cysteine residues in the three domains of PL-C are completely conserved in all other chitin-binding domains.

The complete amino acid sequence of chitinase-B from the leaves of pokeweed (Phytolacca americana).

The complete amino acid sequence of pokeweed leaf chitinase-B (PLC-B) has been determined by first sequencing all 19 tryptic peptides derived from the reduced and S-carboxymethylated (RCm-) PLC-B and then connecting them by analyzing the chymotryptic peptides from three fragments produced by cyanogen bromide cleavage of RCm-PLC-B. PLC-B consists of 274 amino acid residues and has a molecular mass of 29,473 Da. Six cysteine residues are linked by disulfide bonds between Cys20 and Cys67, Cys50 and Cys57, and Cys159 and Cys188. From 58-68% sequence homology of PLC-B with five class III chitinases, it was concluded that PLC-B is a basic class III chitinase.

Purification and characterization of three mitogenic lectins from the roots of pokeweed (Phytolacca americana).

Three mitogenic lectins, designated PL-A, PL-B, and PL-C, were purified from the roots of pokeweed (Phytolacca americana) using Q-Sepharose column chromatography followed by gel filtration on Sephadex G-75, hydrophobic chromatography on Butyl-Toyopearl, and FPLC on a Mono-Q column. PL-A, PL-B, and PL-C are acidic proteins having isoelectric points of 4.35 and their apparent molecular masses were 22, 48, and 21 kDa by SDS-polyacrylamide gel electrophoresis in the presence of 2-mercaptoethanol, respectively. The three lectins have similar amino acid compositions rich in half-cystine and similar N-terminal sequences, indicating that they are homologous proteins. Identical sequences of N-terminal regions and six corresponding tryptic peptides in PL-A and PL-B suggested that PL-A may be an N-terminal half fragment of PL-B. Although all of three lectins have mitogenic activities, PL-B is a mitogenic lectin with the most potent hemagglutinating and mitogenic activities, and PL-C has almost no hemagglutinating activity.

Effects of chemical modification of arginine residues outside the active site cleft of ricin A-chain on its RNA N-glycosidase activity for ribosomes.

Ricin A-chain, a protein that inactivates ribosomes by a specific RNA N-glycosidase activity, has been shown to be inactivated by chemical modification of a few arginine residues. When two or fewer arginine residues in the A-chain were modified with [14C]phenylglyoxal, arginines at positions of 193, 196, 213, and 234/235 were found to be modified, from amino acid compositions and radioactivities of the modified peptides that were obtained by cyanogen bromide cleavage followed by tryptic and chymotryptic digestion. All these arginines have side chains outside the active site cleft; the side chain of Arg213 is adjacent to the edge of the cleft, while other modified arginines are located on the opposite side of the cleft. Kinetic analysis showed that the modification of two arginine residues caused a 8-fold loss in kcat with a 3-fold increase in Km, suggesting that this modification mainly decrease the rate of depurination with an additional effect on the affinity for ribosomes. Neither the environment of tryptophan 211 at the bottom of the cleft nor an interaction of adenine with the cleft was changed by this modification, as judged by fluorescence spectroscopy, suggesting that a conformational change of the catalytic site does not occur upon the modification. These results, taken together with other works, suggest that some of the above arginine residues outside the active site cleft may additively contribute to the catalysis of depurination and/or the initial formation of the A-chain/ribosome complex.

The complete amino acid sequence of chitinase-a from the seeds of rye (Secale cereal).

The complete amino acid sequence of rye seed chitinase-a (RSC-a) has been analyzed. RSC-a was cleaved with cyanogen bromide and the resulting three fragments, CB1, CB2, and CB3, were separated by gel filtration. The amino acids of the N-terminal fragment CB1 were sequenced by analyzing the peptides produced by digestion with trypsin, lysylendopeptidase, or pepsin of reduced S-carboxymethylated or S-aminoethylated CB1. The sequences of fragments CB2 and CB3 were established by sequencing the tryptic peptides from reduced S-carboxymethylated CB2 and CB3, and by aligning them with the sequence of rye seed chitinase-c (RSC-c) to maximize sequence homology. The complete amino acid sequence of RSC-a was established by connecting these three fragments. RSC-a consists of 302 amino acid residues including hydroxyproline residues, and has a molecular mass of 31,722 Da. RSC-a is basic protein with a cysteine-rich amino terminal domain, indicating that this enzyme belongs to class I chitinases. The amino acid sequence of RSC-a showed that the sequence from Gly60 to C-terminal Ala302 in this enzyme corresponds to that of RSC-c belonging to class II chitinases with 92% identity, and that RSC-a has high similarity to other plant class I chitinases but a longer hinge region and an extra disulfide bond.

The complete amino acid sequence of chitinase-c from the seeds of rye (Secale cereal).

The complete amino acid sequence of rye seed chitinase-c (RSC-c) has been analyzed. This was done by first sequencing the tryptic peptides from RCm-RSC-c and then connecting them by analyzing the peptides produced by digestions with lysylendopeptidase and Staphylococcus aureus V8 protease of RCm-RSC-c, and by chymotryptic digestion and formic acid cleavage of S. aureus V8 protease peptides. RSC-c consists of 243 amino acid residues and has a molecular mass of 26,093, and has 92% sequence homology with barley seed basic chitinase which lacks a Cys-rich domain. Cys204 is free and six cysteine residues are linked by disulfide bonds between Cys23 and Cys85, Cys97 and Cys105, and Cys223 and Cys236.

Brefeldin A protects ricin-induced cytotoxicity in human cancer KB cell line, but not in its resistant counterpart with altered Golgi structures.

Brefeldin A (BFA), an isoprenoid fungal metabolite, dramatically disrupts intracellular protein transport and protein secretion. BFA protects cells from the cytotoxicity of a plant toxin, ricin or pseudomonas toxin, but not that of diphtheria toxin (Yoshida et al., 1991. Expt. Cell Res., 192: 389-395.). In this study, we examined whether BFA could differentially change the cytotoxicity of ricin between BFA-sensitive cells and BFA-resistant cells. As a BFA-resistant cell line, we used a resistant cell line, KB/BF2-2, derived from BFA-sensitive human cancer KB cells. BFA treatment caused the disappearance of typical Golgi cisternae and the concomitant appearance of dilated vesicles in the cytoplasm in KB cells. By contrast, KB/BF2-2 cells had already altered Golgi structures with poor development of cisternae and also many vesicles in the absence of BFA, and BFA treatment did not further induce the morphological changes. Although a plasma membrane-specific marker protein, alpha-adaptin, was localized similarly in KB/BF2-2 as KB, Golgi specific markers such as beta-cop and gamma-adaptin were distributed in the cytoplasmic small vesicles as well as Golgi compartments in KB/BF2-2 cells in the absence of BFA, and the mutant cells showed no apparent changes in the distribution even when exposed to BFA. Ricin inhibited protein synthesis in KB and KB/BF2-2 to similar levels while pretreatment of KB cells with BFA at 0.1 microgram/ml almost completely reversed the inhibitory effect of ricin. By contrast, the pre-exposure of KB/BF2-2 cells to 1.0 microgram/ml BFA only partially rescued the ricin-induced inhibition of protein synthesis. Exposure to BFA at 30 min before ricin addition or at 0 min with ricin rescued the protein synthesis inhibition, but no rescue occurred when BFA was added 30 min after ricin addition. BFA could not rescue the protein synthesis inhibition by another toxin, diphtheria toxin. Our results suggest that BFA-resistant mutation causes a specific change in the endocytic membrane traffic of ricin in human cells, and also that cytotoxicity of diphtheria toxin does not share a common pathway of the intracellular transport with that of ricin.

The complete amino acid sequence of ribonuclease from the seeds of bitter gourd (Momordica charantia).

The complete amino acid sequence of ribonuclease (RNase MC) from the seeds of bitter gourd (Momordica charantia) has been determined. This has been achieved by the sequence analysis of peptides derived by enzymatic digestion with trypsin, lysylendopeptidase, and chymotrypsin, as well as by chemical cleavage with cyanogen bromide. The protein contains 191 amino acid residues and has a calculated molecular mass of 21,259 Da. Comparison of this sequence with sequences of the fungal RNases, RNase T2, and RNase Rh, revealed that there are highly conserved residues at positions 32-38 (TXHGLWP) and 81-92 (FWXHEWXKHGTC). Furthermore, the sequence of RNase MC was found to be homologous to those of Nicotiana alata S-glycoproteins involved in self-incompatibility sharing 41% identical residues.

N-acetyl-D-glucosamine-asparagine structure in ribosome-inactivating proteins from the seeds of Luffa cylindrica and Phytolacca americana.

Glycosylation-site-containing peptides were isolated from the proteolytic digests of luffin-a, luffin-b, PAP-S and CNBr-fragments of PAP-S by reverse-phase HPLC, and their amino acid compositions and sequences were analyzed. Six peptides were obtained from luffin-a, and three each from luffin-b and PAP-S. All of these peptides were negative toward the phenol-H2SO4 reaction and gave only N-acetyl-D-glucosamine in gas chromatography after methanolysis and reacetylation. Amounts of N-acetyl-D-glucosamine in these peptides were determined as D-glucosamine to be approximately one mol per peptide by an amino acid analyzer after HCl hydrolysis. Based on these results we concluded that Asn residues at positions of 28, 33, 77, 84, 206, and 227 in luffin-a, of 2, 78, and 85 in luffin-b, and of 10, 44, and 255 in PAP-S were glycosylated with only GlcNAc, and contained one residue per site.

The complete amino acid sequence of antiviral protein from the seeds of pokeweed (Phytolacca americana).

The complete amino acid sequence of antiviral protein from the seeds of pokeweed (Phytolacca americana) has been determined. This has been done by the sequence analysis of peptides derived by enzymatic digestion with trypsin, pepsin, and lysylendopeptidase, as well as by chemical cleavage with cyanogen bromide. The protein consists of 261 amino acid residues containing two disulfide bonds and has a calculated molecular mass of 29167 Da. The two disulfide bonds connect Cys-34 to Cys-258 and Cys-84 to Cys-105. Comparison of this sequence with the sequence of the ricin A-chain shows that there are identical residues at 76 positions in the two molecules (30% identity), having an extended region of highly conserved sequence at positions 170-183 (IQMXSEAARFXYIE). In contrast, the internal regions at positions 77-119 and 141-169 and the C-terminal 15 amino acid residues are less homologous in the two proteins.

Complete amino acid sequence of luffin-a, a ribosome-inactivating protein from the seeds of sponge gourd (Luffa cylindrica).

The complete amino acid sequence of luffin-a has been determined. Twenty-two peptides were isolated from the tryptic digest of luffin-a and sequenced employing the DABITC/PITC double coupling method. Overlaping of these peptides was achieved by analyzing the chymotryptic peptides or CNBr-fragments of luffin-a and their S. aureus V8 protease peptides. Luffin-a consists of 248 amino acid residues and its relative molecular mass is calculated to be 27,021 Da, excluding the attached sugar chains reasoned to be present at each Asn residue of positions 28, 33, 77, 84, 206, and 227. A comparison with the sequence of ricin A-chain showed 33% sequence identity indicating that these proteins are homologous.