Expression of a synthetic gene encoding the anticoagulant-antimetastatic protein ghilanten by the methylotropic yeast Pichia pastoris.

Ghilantens are a family of cysteine-rich inhibitors of the clotting enzyme, factor Xa, that are produced in the salivary glands of the South American leech Haementeria ghilianii. In this study, a gene, designed from the amino acid sequence of a specific ghilanten isoform, was assembled from eight double-stranded oligonucleotide fragments. A yeast expression plasmid, pPIC9HG-2, was constructed by making an inframe fusion of the ghilanten-coding sequences with the region encoding the pre-pro alpha-mating factor signal sequence for secretion. The expression of ghilanten in pPIC9HG-2 was under the control of the methanol-inducible, alcohol oxidase (AOX1) promoter. Pichia pastoris yeast strains KM 71 and SMD 1168 were transformed with linearized pPIC9HG-2 to target integration of the plasmid to the chromosomal 5'-AOX1 locus via homologous recombination. Both strains yielded His+ transformants that secreted a potent anticoagulant activity into the medium. Product yield was improved by using buffered media (pH 6.0) supplemented with either casamino acids or a mixture of yeast extract and peptone. The protease-deficient strain, SMD 1168, secreted about a twofold higher level of r-ghilanten than KM 71. Significant clonal variation in the expression of r-ghilanten was found among the His+ transformants. A high producing clone was selected for production at the 2-liter shake flask and 10-liter bioreactor scales. r-Ghilanten was recovered from the fermentation broths in a single step by heparin Sepharose affinity chromatography. Protein sequence analysis of the amino terminus showed that the correct processing to yield mature ghilanten varied with the fermentation conditions.

Potent inhibition of human immunodeficiency virus by MDL 101028, a novel sulphonic acid polymer.

MDL 101028, a novel biphenyl disulphonic acid urea co-polymer was designed and synthesised as a heparin mimetic. This low molecular weight polymer showed potent inhibition of human immunodeficiency virus type 1 (HIV-1) replication in a number of host-cell/virus systems, including primary clinical isolates of the virus cultured in human peripheral blood mononuclear cells (PBMCs). When compared with the heterogeneous polysulphated molecules, heparin and dextran sulphate, this chemically defined compound showed equivalent antiviral activity with 50% inhibitory concentrations (IC50s) in the range 0.27-3.0 micrograms/ml in the host-cell/virus systems tested. MDL 101028 also inhibited the replication of HIV type 2 and the simian immunodeficiency virus (SIV), as well as HIV-1 variants resistant to reverse transcriptase inhibitors. Virus growth was blocked when exposure of T-lymphocytes to MDL 101028 was restricted to the virus absorption stage, or even in whole blood conditions. MDL 101028 did not irreversibly inactivate virions, and in contrast to heparin, did not inhibit the attachment of radiolabelled HIV-1 to CD4+ T-cells. MDL 101028 blocked HIV-induced cell-to-cell fusion and this activity appears to explain the mechanism of its antiviral action. The antiviral evaluation of discrete oligomer molecules of MDL 101028 showed that a polymer chain length of six repeating units had optimal potency. The lack of anticoagulant properties and significant antiviral activity in whole blood may allow the development of MDL 101028 as a treatment of HIV infections.

Specific interaction of 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid with human cellular CD4.

We recently demonstrated that 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) prevented the infection of T cells by human immunodeficiency virus type-1 (Cardin et al., J. Biol. Chem. 266, 13355, 1991). In the present study we have used a panel of monoclonal antibodies (mabs) against a variety of human leukocyte antigens to characterize the interaction of DIDS by flow cytometry with various T cell surface molecules. DIDS blocked the specific immunoreactivity of mabs OKT4A and Leu 3A with CD4 on human leukemic T cells (JM) and human mononuclear lymphocytes with an IC50 approximately 30 microM. The membrane distal (D1) and proximal (D3 and D4) domains of CD4 remained blocked for up to 5 hr of culture and returned to control levels of expression after 24 hr, reflecting the rate of membrane turnover of the CD4-DIDS complex. The binding frequencies (% positive) for anti-CD2, -CD3, -CD5, -CD6, -CD7, -CD8, -CD11a, -CD14, -CD18, -CD19, -CD45, -T cell receptor, and -HLA-DR were not significantly affected. However, there was a partial reduction in the antigen density of CD2, CD5, CD8, and CD11b. The selective interaction of DIDS with CD4 suggests that antagonism of the virus receptor may account in part for the antiviral properties of the stilbene disulfonate.

Crystallographic structure of human gamma-thrombin.

In an effort to prepare crystals and determine the structure of alpha-thrombin complexed to a synthetic peptide inhibitor (MDL-28050) of the hirudin 54-65 COOH-terminal region, it was discovered that the crystals were not those of the complex but of gamma-thrombin. Gel electrophoresis studies revealed that autolytic degradation had occurred prior to crystallization. NH2-terminal sequence analysis of these autolytic fragments confirmed the gamma-thrombin product (cleavages at Arg75-Tyr76 and/or Arg77A-Asn78, and Lys149E-Gly150; chymotrypsinogen numbering) with a minor amount of another autolysis product, beta-thrombin (first two cleavages only). The final structure has an R-factor of 0.156 for 7.0-2.5-A data, and includes 186 water molecules. A comparison of gamma-thrombin with the thrombin structure in the alpha-thrombin-hirugen complex revealed that the two structures agreed well (r.m.s. delta = 0.39 A for main chain atoms). These structures possess uninhibited active sites where the disposition of the catalytic triad residues is nearly identical. The electron density in the vicinity of the gamma-thrombin cleavage regions is poor, and only becomes well-defined several residues prior to and after the actual cleavage sites. The extensive disorder evoked by beta-cleavage(s) in the Lys70-Glu80 loop region indicates that this part of the molecule is severely disrupted by autolysis and is the reason exosite functions are dramatically impaired in beta-and gamma-thrombin. Since autolysis did not lead to a major reorganization of the folded structure of alpha-thrombin, the likely structural features of the interaction of thrombin substrate with thrombin enzyme during beta-cleavage have been modeled by docking the exosite region of one molecule at the active site of another.

Identification of a 63-kDa serum protein that binds somatostatin and gastrin-releasing peptide but not bombesin.

A 63-kDa serum protein was identified that bound somatostatin and gastrin-releasing peptide (GRP) but not bombesin. The 63-kDa protein was detected by its ability to compete with the receptor for GRP in a receptor binding assay. This interaction could be inhibited by the addition of somatostatin, producing a higher and more accurate calculated affinity for the binding of GRP to its receptor. Somatostatin did not affect the affinity of the receptor for bombesin. Specificity of the 63-kDa protein for analogs of somatostatin, GRP, and bombesin was determined by competition with 125I-GRP and 125I-somatostatin. A tripeptide motif consisting of an aryl-hydrophobic-basic amino-acid structure in residues 15-17 of GRP (Tyr-Pro-Arg) and residues 7-9 of somatostatin (Phe-Trp-Lys) was implicated in binding. This tripeptide binding motif is not present in bombesin. That residues 15-17 of GRP are highly conserved suggests that its interaction with the 63 kDa serum protein may be physiological.

Structure of human des(1-45) factor Xa at 2.2 A resolution.

The structure of a large molecular fragment of factor Xa that lacks only a Gla (gamma-carboxyglutamic acid) domain (N-terminal 45 residues) has been solved by X-ray crystallography and refined at 2.2 A resolution to a crystallographic R-value of 0.168. The fragment identity was clearly established by automated Edman degradation. X-ray structure analysis confirmed the biochemical characterization and also revealed that the N-terminal epidermal growth factor (EGF)-like domain is flexibly disordered in crystals. The second EGF module, however, is positionally ordered making contacts with the catalytic domain. The overall folding of the catalytic domain is similar to that of alpha-thrombin, excluding the insertion loops of the latter with respect to simpler serine proteinases. The C-terminal arginine of the A-chain interacts in a substrate-like manner with the S1 specificity site of the active site of a crystallographically neighboring molecule. Based on this interaction and the structure of D-PheProArg methylene-thrombin, a model of the commonly used dansylGluGlyArg methylene inhibitor-factor Xa interaction is proposed. The region of factor Xa corresponding to the fibrinogen recognition site of thrombin has a reversed electrical polarity to the anion binding fibrinogen recognition site of thrombin but possesses a site similar to the Ca2+ binding site of trypsin and other serine proteinases. The structure of the C-terminal EGF domain of factor Xa is the first to be determined crystallographically. Its folding has been comprehensively compared with similar domains determined by NMR. Although the A-chain makes 44 contacts at less than 3.5 A with the catalytic domain, only 16 involve the EGF module. In addition, the A-chain makes 30 intermolecular contacts with a neighboring catalytic domain.

Mechanism of enhanced kinin release from high molecular weight kininogen by plasma kallikrein after its exposure to plasmin.

When purified high molecular weight kininogen was incubated with streptokinase-activated plasmin and kallikrein, a larger amount of kinin was released than would have been predicted from the effect of either enzyme alone. To determine the mechanism of this enhancement, high molecular weight kininogen was digested sequentially with these enzymes, and the rates of kinin release and sites of cleavage were determined. Conversion of 133 kd native high molecular weight kininogen to two-chain 112 kd or 102 kd derivatives by plasmin more than doubled the rate of kinin release by kallikrein. Conversely, digestion of high molecular weight kininogen by kallikrein and then plasmin did not enhance the rate of kinin release. The kallikrein cleavage points that provided 112 kd and 102 kd two-chain high molecular weight kininogen were after residues 437 (Arg-Lys) and 389 (Arg-Ser), whereas those for plasmin were after 438 (Lys-His) and 389 (Arg-Ser). epsilon-Aminocaproic acid, which competes for lysine residues that are critical to the binding of plasminogen or plasmin to substrates, inhibited the digestion of high molecular weight kininogen by plasmin, which is consistent with the evidence that the 438-439 Lys-His was a primary site of plasmin attack on high molecular weight kininogen. Furthermore, this cleavage was observed when plasminogen activation was induced in normal and in prekallikrein or Hageman factor-deficient plasmas. We suggest that the generation of fibrinolytic activity in blood could result in enhanced kinin release by kallikrein in regions of inflammation as a result of the collaborative actions of plasmin and kallikrein on high molecular weight kininogen.

Heparin binding properties of the carboxyl terminal domain of [A103,106,108] antistasin 93-119.

Antistasin is a 119 amino acid protein with anticoagulant, antimetastatic and heparin-binding properties derived from the salivary glands of the leech Haementaria officinalis (1). This protein contains a specific consensus sequence for heparin binding at its carboxyl terminal end and a region between residues 32 and 48 putatively involved in glycosaminoglycan interactions. The cyclic peptide antistasin 37-48 (C-P-H-G-F-Q-R-S-R-Y-G-C) and the carboxyl terminal fragment [A103,106,108] antistasin 93-119 (P-N-G-L-K-R-D-K-L-G-A-E-Y-A-E-A-R-P-K-R-K-L-I-P-R-L-S) were synthesized by solid-phase peptide chemistry and their interactions with 125I-labeled heparin were investigated. Heparin binding to [A103,106,108] antistasin 93-119 was specific and saturable as binding was blocked by addition of the unlabeled glycosaminoglycan. The rank order of potency of various glycosaminoglycans in blocking 125I-labeled heparin binding to [A103,106,108] antistasin 93-119 was dextran sulfate greater than heparin much greater than dermatan sulfate greater than or equal to chondroitin sulfate A and C indicating a specificity of the peptide for the glycosaminoglycan structure. Moreover, heparin binding increased linearly with increasing salt and was optimal at 0.15 M NaCl and physiological pH. In contrast, binding of heparin to the basic peptide antistasin 37-48 decreased linearly as the ionic strength of the medium was increased to physiological concentration (0.15 M) thus showing a greater specificity of heparin for [A103,106,108] antistasin 93-119. These studies indicate that residues 93-119 of antistasin mediate this inhibitor's interaction with heparin.

Trans-repressor activity of nuclear glycosaminoglycans on Fos and Jun/AP-1 oncoprotein-mediated transcription.

Heparin blocks the phorbol ester-induced progression of nontransformed cells through the G0/G1 phase (Wright, T.C., L.A. Pukac, J.J. Castellot, M.J. Karnovsky, R.A. Levine, H.-Y. Kim-Park, and J. Campisi. 1989. Proc. Natl. Acad. Sci. USA. 86: 3199-3203) or G1 to S phase (Reilly, C. F., M. S. Kindy, K. E. Brown, R. D. Rosenberg, and G. E Sonenshein. 1989. J. Biol. Chem. 264:6990-6995) of the cell cycle. Cell cycle arrest was associated with decreased levels of stage-specific mRNAs suggesting transcriptional regulation of cell growth. In the present report, we show that heparin selectively repressed TPA-inducible AP-1-mediated gene expression. Heparin-induced trans-repression was observed in primary vascular smooth muscle cells, as well as in the transformed HeLa cell line and in nondifferentiated F9 teratocarcinoma cells. Inhibition of AP-1-mediated trans-activation occurred with heparin and pentosan polysulfate but not with chondroitin sulfate A or C. Heparin-binding peptides or heparitinase I addition to nuclear lysates of heparin-treated cells allowed enhanced recovery of endogenous AP-1-specific DNA binding activity. We propose a model in which nuclear glycosaminoglycans play a trans-regulatory role in altering the patterns of inducible gene expression.

Specific inhibition of binding of antistasin and [A103,106,108] antistasin 93-119 to sulfatide (Gal(3-SO4)beta 1-1Cer) by glycosaminoglycans.

Leech-derived antistasin is a potent anticoagulant and antimetastatic protein that binds sulfatide (Gal(3-SO4)beta 1-1Cer) and sulfated polysaccharides. In this study, the synthetic fragment [A103,106,108] antistasin 93-119, which corresponds to the carboxyl terminus, showed specific and saturable binding to sulfatide. Binding was competitively blocked by glycosaminoglycans (GAGs) in the order: dextran sulfate 5000 congruent to dextran sulfate 500,000 greater than heparin greater than dermatan sulfate much greater than chondroitin sulfates A and C. This rank order of inhibitory potency was identical to that observed with whole antistasin. We suggest that residues 93-119 of antistasin represent a critical domain for binding GAGs and sulfated glycolipids.

Demonstration that [A103,106,108] antistasin 93-119 inhibits the specific binding of antistasin to sulfatide [Gal(3-SO4)beta 1-1Cer].

Antistasin is a 119 amino acid heparin-binding protein from the leech Haementaria officinalis which has anticoagulant and antimetastatic properties. A series of peptides representing the basic amino acid-rich domains of the amino- and carboxyl-terminal regions of the inhibitor were synthesized by solid-phase peptide chemistry and their ability to bind sulfated glycolipids was investigated. The findings show that [A103,106,108] antistasin 93-119 has high affinity for sulfatide and inhibits the specific interaction of whole antistasin with [Gal(3-SO4)beta 1-1Cer]. We conclude that the 93-119 region is a critical domain that mediates the interaction of antistasin with sulfated glycolipids.

Stilbene disulfonic acids. CD4 antagonists that block human immunodeficiency virus type-1 growth at multiple stages of the virus life cycle.

The stilbene disulfonic acids 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid and, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid bound the variable-1 immunoglobulin-like domain of CD4 on JM cells. The interaction blocked the binding of the anti-CD4 monoclonal antibody OKT4A and the envelope glycoprotein gp120 of the human immunodeficiency virus type-1 (HIV-1). DIDS inhibited the acute infection of CD4+ cells by HIV-1 with a potency (IC50 approximately 30 microM) similar to that which blocked gp120 binding (IC50 approximately 20 microM) to the cellular antigen. Pretreating uninfected CD4+ C8166 cells with DIDS blocked their fusion with chronically infected gp120+ cells. DIDS covalently and selectively modified lysine 90 of soluble CD4 and abolished the gp120-binding and antiviral properties of the recombinant protein. When added to cells productively infected with HIV-1, DIDS blocked virus growth and cleared cultures of syncytia without inhibiting cellular proliferation. The stilbene disulfonic acids are a novel class of site-specific CD4 antagonists that block multiple CD4-dependent events associated with acute and established HIV-1 infections.

Studies on the anticoagulant, antimetastatic and heparin-binding properties of ghilanten-related inhibitors.

The purpose of this study was to investigate the structure-activity relationships of ghilanten, an anticoagulant-antimetastatic protein of the South American leech Haementeria ghilianii. Five sequence-related variants of ghilanten, termed P1-P5, were purified and were shown to potently block the active-site hydrolysis of methoxycarbonyl-D-cyclohexylglycyl-glycyl-arginine-p-nitroanilide acetate by the human blood coagulation enzyme factor Xa; inhibition was rapid and stoichiometric. The amino acid sequence of P5 revealed a consensus sequence for heparin-binding at the carboxy-terminus. A synthetic peptide homologous to this region (93P-N-G-L-K-R-D-K-L-G-C-E-Y-C-E-C-R-P-K-R-K-L-I-P-R-L-S119) bound 125I-labelled heparin maximally at physiological pH and salt concentration. When administered intravenously to mice, the peptide suppressed lung metastases although less potentially than whole ghilanten. These findings suggest that the carboxy-terminal heparin-binding region may play a role in the antimetastatic action of the inhibitor.

Characterization of the murine pancreatic receptor for gastrin releasing peptide and bombesin.

The murine pancreatic receptor for bombesin and gastrin releasing peptide (GRP) has been characterized. Analysis of the binding of 125I-GRP to membranes indicates a single class of sites (10(-13) mol/mg protein) with Kd of 43 pM. A 70 kDa membrane protein was cross-linked to 125I-GRP by bis(sulfosuccinimidyl) suberate; labeling was blocked by GRP, GRP (14-27), AcGRP(20-27), GRP(18-27), bombesin and ranatensin, was partially blocked by [Leu13 psi (CH2NH)Leu14]bombesin and was unaffected by GRP(21-27) and GRP(1-16). The IC50 values for the competitive displacement of 125I-GRP from intact membranes by these peptides were similar to those obtained by the cross-linking experiments showing that the 70 kDa protein is the GRP receptor. The GRP receptor is G-protein coupled; divalent cations are required for high-affinity binding and nonhydrolyzable GTP analogs decrease receptor affinity. In minced pancreas, GRP caused a dose-dependent increase in inositol phosphates implicating phospholipase C in signal transduction. We suggest that the murine pancreatic receptor for bombesin/GRP is a 70 kDa membrane protein, is associated with a G-protein and stimulates phosphatidylinositol turnover.

Molecular design and modeling of protein-heparin interactions.

The methods and approaches taken to investigate heparin-apoE peptide interactions have involved a series of steps, including (1) identification of the heparin-binding domains of apoE, (2) determination of the minimal amino acid sequence regions involved in heparin binding, heparin-induced conformational changes, and stability of apoE peptide structures in solution, (3) modeling of these peptide and oligosaccharide structures, and (4) examination of their behavior during molecular dynamics calculations to determine if the modeled complexes simulate the results of the solution study. The heparin-binding regions of apoE were determined by fragmentation of the protein and identification of the heparin-binding fragments by ligand-blotting procedures using 125I-labeled heparin. Studies with synthetic peptide fragments of various lengths and dot-blot procedures with 125I-labeled heparin identified the minimal residues critical for heparin-binding and CD studies established the prominent secondary structures of these domains. These studies also showed that heparin binds to the apoE(211-243) and apoE(129-169) regions to induce and stabilize beta-strand and alpha-helical peptide conformations. Secondary structure algorithms were used to identify the specific residues with the highest probabilities of forming alpha-helix and beta-strand structures. Based on the predictive algorithms, the apoE(211-234) and apoE(129-159) structures were built using the Insight program and their molecular interactions with various heparin oligosaccharide models were investigated by molecular dynamics. In agreement with the solution studies in the presence of salt, the molecular dynamics studies showed that the oligosaccharides stabilized the beta-strand and alpha-helical peptide configurations against simulated thermal denaturations. Further modeling studies are in progress to examine the mechanism of the heparin-induced increase in ordered structure of these peptides.

Curtatoxins. Neurotoxic insecticidal polypeptides isolated from the funnel-web spider Hololena curta.

Three polypeptide neurotoxins (curtatoxins) were isolated from the venom of the spider Hololena curta by reverse-phase high performance liquid chromatography, gel permeation, and ion-exchange chromatography. The purified toxins induced an immediate paralysis in the cricket Acheta domestica that resulted in desiccation and death of the insect within 24-48 h (LD50 congruent to 4-20 micrograms/g); this toxic effect is consistent with irreversible presynaptic neuromuscular blockade. Curtatoxins are a class of sequence-related, cysteine-rich, carboxyl-terminal amidated polypeptides of 36 to 38 amino acid residues. The cysteine residues are conserved at identical sequence positions among these polypeptides and form 4 intramolecular disulfide bonds. Hydropathy calculations show that the toxins have an internal hydrophobic region flanked by hydrophilic and oppositely charged amino- and carboxyl-terminal ends. By analogy to other cysteine-rich arthropod venom proteins, the folded structure of the curtatoxins is likely important for their target specificity and mode of action at the neuromuscular junction.

Amino acid sequence of ghilanten: anticoagulant-antimetastatic principle of the South American leech, Haementeria ghilianii.

This study reports the amino acid sequence of ghilanten, an anticoagulant-antimetastatic principle of the hematophagous leech, Haementeria ghilianii. Ghilanten consists of 119 amino acids with twenty cysteines and a consensus sequence for heparin-binding at its carboxyl-terminus. Arginine-34 represents the reactive residue involved in the active-site inhibition of trypsin and Factor Xa. Immunoreactivity data suggest that heterogeneity among ghilantens is due in part to amino acid substitutions at their carboxyltermini.

Ghilantens: anticoagulant-antimetastatic proteins from the South American leech, Haementeria ghilianii.

Five proteins with anticoagulant and antimetastatic activities were isolated from the salivary glands of the Amazon leech, Haementeria ghilianil. These proteins, designated ghilantens, were co-purified on DEAE-cellulose and heparin-agarose, and were purified by microbore C-18 reverse-phase HPLC. Each variant had a similar molecular weight (18,000), amino acid composition, and a blocked amino terminus. Ghilantens caused a dose-dependent prolongation of the prothrombin time of normal human plasma and blocked the factor Xa-mediated hydrolysis of methoxycarbonyl-D-cyclohexylglycyl-glycl-arginine-p-nitro anillide acetate. Ghilantens were quantitatively absorbed to bovine factor Xa-AffiGel-15 and were eluted with 0.1 mol/L benzamidine, an active-site reversible inhibitor of factor Xa. These findings show that ghilantens can form a reversible association with the enzyme. When administered intravenously to mice by tall vein injection, ghilantens potently suppressed lung metastases of B16-F10 melanoma cells. These findings suggest that ghilantens may have therapeutic value in the treatment of metastatic disease.

High-sensitivity amino acid analysis by derivatization with O-phthalaldehyde and 9-fluorenylmethyl chloroformate using fluorescence detection: applications in protein structure determination.

An amino acid analysis method using a commercially available analyzer that accurately quantitates protein-derived amino acids in the 10-100 pmol range is described. The method utilizes the robotic capability of the analyzer's autosampler to perform precolumn derivatization of both primary and secondary amino acids with o-phthalaldehyde and 9-fluorenylmethyl chloroformate, respectively. The derivatized amino acids are then separated on a C-18 reverse-phase amino acid column and quantitated in a single run by fluorescence detection. The characterization of beta-lactoglobulin and two tryptic peptides from the bacterial enzyme diaminopimelic acid epimerase is used to demonstrate the sensitivity and utility of this method.