Genes for Biologically Active Proteins

The invention relates to a new member of the gene family which has hitherto comprised the genes for the proteinase inhibitors antithrombin III, .alpha..sub.1 -proteinase inhibitor (.alpha..sub.1 -antitrypsin), antichymotrypsin, contrapsin and .alpha..sub.2 -antiplasmin, and by angiotensinogen.

FIG. 1 is an amino acids sequence of the present invention.

FIG. 2 is a nucleotide sequence of the present invention.

The gene which has been found codes for a protein with the amino acid sequence I (annex). Its coding strand has 2081 nucleotides, 636 of these being located after the stop codon TAG (DNA sequence I). In the figure, the nontranslated region is represented as an unshaded block, and the structural gene is represented by shading. The DNA sequence I contains an additional two nucleotides upstream of the codon for the N-terminal amino acid (glycine), which presumably code for the final amino acid of a prosequence (by analogy with the proteinase inhibitors AT BM and heparin cofactor II, it is possible to conclude that glycine is the N-terminal amino acid of the "mature" new proteinase inhibitor: I. Witt et al., Thrombosis Research 32 (1983) 513-518; M. J. Griffith et al., J. Biol. Chem. 260 (1985) 2218-2225).

Amino acid sequence I allows those skilled in the art to prepare antibodies in a known manner, by selection of oligopeptides from this amino acid sequence I, to load an antibody column with them, and to use this column to isolate the complete protein from biological material.

On the other hand, it is possible to use the gene or the cDNA sequence I to express the protein in suitable host organisms.

It is furthermore possible to derive from the amino acid sequence I modified genes or partial genes which lead to modified proteins in which individual amino acids have been exchanged, deleted or introduced. It is also possible in the construction of synthetic genes to provide new recognition sites for restriction enzymes, which permit further modifications of the amino acid sequence. It is also possible to take into account in the construction of synthetic genes the fact that, compared with higher organisms, microbial host organisms in some cases prefer other codons.

The new protein exhibits homologies with the abovementioned proteinase inhibitors, at the level both of the DNA and of the amino acid sequence. For this reason, the gene is also suitable for the preparation of analogs of proteinase inhibitors by replacement of the nucleotides coding for the "active center" of the new protein by the appropriate nucleotides coding for the "active centers" of the known proteinase inhibitors. The "active center" of the new protein comprises the amino acids Leu-Ser (amino acids 444 and 445 of amino acid sequence I), corresponding to the nucleotide sequence CTG TCC.

Thus, in this type of construction of analogs of the known proteinase inhibitors it is possible, by the "modular principle", for a partial gene I which codes for the amino acid sequence upstream of the active center to be combined with a partial gene II which codes for the amino acid sequence downstream of the active center, with interpolation of a gene fragment which codes for the appropriate active center. In this process it is possible to make use of the following recognition sites for restriction enzymes in the DNA sequence I:

The modification of humane .alpha..sub.1 -antitrypsin has already been disclosed (S. Rosenberg et al., Nature 312 (1984) 77-80, compare A. Maelicke, Nachr. Chem. Tech. Lab. 32 (1984) 1070; M. Courtney et al., Nature 313 (1985) 149-151), in each case the active center having been modified but the amino acid sequences upstream and downstream of the active center remaining unchanged. In contrast, the new products obtained according to the invention have amino acid sequences upstream and downstream of the active center which correspond to the new proteinase inhibitor and, where appropriate, its modifications, but contain the active center of another proteinase inhibitor. Thus the invention permits a multiplicity of modifications of such proteins, all of which have virtually the same tertiary structure. Their biological activity is influenced by the active center.

In one embodiment of this invention, a protein with proteinase inhibitor activity is disclosed which has amino acids 1 to 443 and/or 446 to 480 of amino acid sequence I.

The new protein and its analogs have proteinase-inhibitory, in particular thrombin-inhibitory, activity and they influence the coagulation of blood. Thus they can be used as medicaments in a daily dose from about 0.1 to 100 mg. Since, as is known, proteins are broken down in the stomach, the proteins according to the invention must be administered in a medicament form which prevents this breakdown, for example by administration in the form of enteric capsules or by parenteral administration.

The cDNA sequence I was obtained by screening of a human liver cDNA bank using the oligonucleotide, obtained by synthesis, of DNA sequence II

This nucleotide sequence was selected with reference to the known cDNA sequence of proteinase inhibitors adjacent to the carboxyl terminal end. It has emerged that the sequence is substantially complementary to the coding strand corresponding to amino acids 469 to 477 of amino acid sequence I.

The methods for the synthesis of oligonucleotides, for the hybridization and for the obtaining of the gene are generally known, as are the procedure for the introduction of the genetic information into host cells and the expression of the coded polypeptide in prokaryotic and eukaryotic expression systems. Prokaryotic cells produce the protein in the non-glycosylated state, whereas eukaryotic systems are able to generate a glycosylated protein. N-Glycosylation can take place at amino acids 30, 169 and 368 of amino acid sequence I.

The modification of DNA sequence I is illustrated below by the example of the introduction of another active center. For this purpose, DNA sequence I is partially cut with endonucleases Sau3A I and AccI, and the short DNA fragment is replaced by a synthetically prepared gene fragment which codes for the following active centers:

(R. Hill et al., Nature 311 (1984) 175-177; M. Courtney et al., loc. cit.; J. Travis et al., Behring Inst. Mitt. 73 (1983) 56-65).

The DNA sequence I can also be modified by addition of a nucleotide sequence coding for a signal peptide according to known methods.

Thus the new gene is also suitable as a starting material for the preparation of new proteins with proteinase-inhibitory activity. These new compounds can also be used as medicaments corresponding to the known proteinase inhibitors which have identical or similar actions.

It is also possible to modify further these new analogs of known proteinase inhibitors by modification of the gene in a known manner, by which means there are obtained proteins in whose amino acid chain amino acids have been replaced, deleted or added to. The invention likewise relates to proteins of this type with proteinase inhibitor activity.

The specific aspects of the invention are illustrated in detail in the examples which follow. Unless otherwise stated, percentages relate to weight.

Frozen human liver biopsy material was powdered under liquid nitrogen in a mortar. The powder was homogenized in a mixer with 4M guanidinium thiocyanate stock solution (J. Chirgwin et al., Biochemistry 18 (1979) 5295-5299), which had been preheated to 70.degree. C., for one minute. The mixture was centrifuged at 10.degree. C. for 10 minutes (Sorvall HB-4 rotor, 8,000 rpm). The supernatants were removed, 0.5 g of cesium chloride was added for each ml of supernatant and the mixture was heated at 60.degree. C. for a few minutes. The resulting solution was then transferred to ultracentrifuge tubes which were one quarter full with a solution comprising 5.7M cesium chloride, 12.5 mM sodium salt of ethylenediaminetetraacetic acid (EDTA, pH 7.5) and 12.5 mM sodium citrate (pH 7.0). The tubes were centrifuged at 20.degree. C. for 17 hours (Beckman SW-28 rotor, 21,000 rpm). The supernatants were removed by suction, and the sediment was suspended in TES buffer (50 mM tris.HCl, 10 mM EDTA, 0.2% (w/v) sodium salt of dodecylsulfate (SDS, pH 7.4)) with heating, and the suspension was extracted once with the same volume of a mixture of chloroform and n-butanol (4:1, v/v). After centrifugation, the aqueous phase was mixed with one tenth of the volume of 3M sodium acetate solution (pH 5.2), and precipitation was carried out with ethanol. After standing at -20.degree. C. for at least two hours, the mixture was centrifuged at 12,000 rpm and 0.degree. C. for 20 minutes, and the sediment was washed with 80% strength ethanol. The dried precipitate was dissolved in 0.1 molar sodium acetate solution (pH 7.0) and reprecipitated with ethanol. The precipitate was, as described above, centrifuged, washed and dried. After redissolving in a buffer solution (0.1M sodium acetate, pH 5.2, 10 mM tris.HCl, pH 7.4, 1 mM EDTA and 0.2% (w/v) SDS), the solution was extracted twice with the same volume of phenol equilibrated with 1M tris.HCl, pH 8.0, and 0.2% (w/v) hydroxyquinoline, and was centrifuged. After extraction once with the same volume of chloroform, and centrifugation, the aqueous phase was mixed with the same volume of a solution of urea (8M) and lithium chloride (4M) and was stored at 0.degree. C. overnight. After centrifugation at 0.degree. C. for 20 minutes (SS 34 rotor, 10,000 rpm), the sediment was taken up in TES buffer, and the solution was mixed with one tenth the volume of 3M sodium acetate solution (pH 5.6), and precipitation with ethanol was carried out. The sediment was centrifuged, washed and dried as described above and finally taken up in buffer solution (50 mM tris.HCl, 1 mM EDTA, 0.1% w/v) SDS, pH 7.5). The mixture was mixed with the same volume of 1M sodium chloride solution, and the poly(A)-RNA was isolated by chromatography twice on oligo-(dT)-cellulose. After addition of sodium acetate solution, the poly(A)-RNA was precipitated with ethanol and finally dissolved at a concentration of 1 .mu.g/.mu.l of buffer solution (1 mM tris.HCl, 0.1 mM EDTA, pH 7.0).

10 .mu.g of poly(A)-RNA in 10 .mu.l of the abovementioned buffer were heated at 70.degree. C. for 3 minutes, cooled rapidly in ice-water, and used for the synthesis of the cDNA. The synthesis of the first strand in a final volume of 100 .mu.l was carried out by the method of M. Wickens et al., J. Biol. Chem. 253 (1978) 2483-2495, making use of .sup.32 P-labeled thymidine triphosphate, with the RNase inhibitor RNasin (100 U per mix; supplied by Biotec) additionally being used. In the synthesis of the second strand (likewise by the method of Wickens et al., loc. cit.), use was made of the Klenow fragment of DNA polymerase from E. coli (100 U/200 .mu.l reaction), and the reaction was carried out at 15.degree. C. for 4 hours and then at 20.degree. C. for 2 hours. The reaction was stopped by extraction with a mixture of equal volumes of phenol and chloroform. The aqueous phase was centrifuged and then fractionated on a 5 ml column containing (.RTM.)SEPHADEX G-100, equilibrated in 20 mM sodium chloride. The fractions containing cDNA were collected and mixed with sodium acetate, and precipitation with ethanol was carried out overnight. To remove the hairpin structures, the dsDNA was treated with 90 U of nuclease S.sub.1 (P-L Biochemicals) in a reaction volume of 250 .mu.l at 37.degree. C. for 30 minutes (Maniatis et al., Molecular Cloning, a Laboratory Manual; Cold Spring Harbor, 1982). The reaction was stopped by extraction with a mixture of equal volumes of phenol and chloroform and, after addition of sodium acetate, the DNA was precipitated with ethanol. The ends of the dsDNA were repaired in a known manner using Klenow polymerase (Maniatis et al., loc. cit.), the reaction was stopped by extraction with a mixture of equal volumes of phenol and chloroform and, after addition of sodium acetate, the DNA was precipitated with ethanol.

For the transformation of E. coli HB 101, standard methods were used for cleavage of the plasmid pUC13 (BRL, Catalogue and Reference Guide, 1983, page 89) with the restriction endonuclease Sma I and treatment with alkaline phosphatase. The ds-cDNA which was obtained was, without further pretreatment, dissolved in buffer (1 mM tris.HCl, pH 7.5, 0.1 mM EDTA) and ligated into the vector pUC13 which had been cleaved with Sma I and phosphorylated.

The transformation into E. coli HB 101 was carried out by described methods (Maniatis et al., loc. cit.). Ampicillin-resistant colonies were blotted onto nitrocellulose filters. Replica plates were treated with 150 .mu.g/ml chloramphenicol, and the colonies were lyzed. The immobilization of the DNA on the nitrocellulose filters was carried out in a known manner (Maniatis et al., loc. cit).

For the in situ hybridization, 52 nitrocellulose filters, each with 300 to 400 colonies, were washed in prewashing solution (Maniatis et al., loc. cit., page 326) at 42.degree. C. for 2 hours, and then batches of 26 filters were prehybridized at 42.degree. C. for 6 hours in 150 ml of the following mixture:

0.9M NaCl

0.18M tris.HCl, pH 8.0

6 mM EDTA

5-fold concentrated Denhardt solution

0.2% (w/v) SDS

200 .mu.g/ml sheared and denatured calf thymus DNA (Sigma)

200 .mu.g/ml yeast RNA (Sigma)

0.5% (v/v) non-ionic surfactant (Nonidet P-40, Sigma)

The hybridization with 10.sup.5 cpm/ml of the probe with DNA sequence II was carried out with the same buffer (at 42.degree. C. for 16 hours). The filters were then washed for 2.times.20 minutes at room temperature (0.9M sodium chloride, 0.09M sodium citrate, pH 7.0) and then washed in the same buffer for 2.times.20 minutes at 33.degree. C. Thereafter the filters were dried and X-ray films were exposed to them at -70.degree. C.

The probe with the DNA sequence II was synthesized by the phosphotriester method. For the hybridization, the oligonucleotide was labeled with .sup.32 P at the 5'-end.

On screening, a recombinant plasmid (pL 10/2) which hybridized very strongly with the oligonucleotide of DNA sequence II and comprised about 1,500 bp of human DNA was isolated. The nucleotide sequence of the cDNA insert was determined by the method of Maxam and Gilbert (Methods in Enzymology 65 (1980) 499-560) as being nucleotides 518-2081 of DNA sequence I.

For 5'-prolongation of the clone pL 10/2, renewed cDNA synthesis with the poly(A)-RNA obtained in Example 1 was carried out:

The oligonucleotide of DNA sequence III

which corresponds to the nucleotide sequence 1051-1064 of the non-coding strand of DNA sequence I was synthesized by the phosphotriester method.

500 pmol of the oligonucleotide III, which had been reacted with polynucleotide kinase and .gamma.-.sup.32 P-labeled ATP, and 10 .mu.g of poly(A)-RNA from Example 1 were heated at 70.degree. C. in 52 .mu.l of buffer (1 mM tris.HCl, pH 7.5; 0.1 mM EDTA, 0.5M KCl) for 3 minutes and then cooled to 43.degree. C. within 30 minutes. The cDNA was synthesized by the method of Gubler and Hoffman, Gene 25 (1983), 263-269, the oligonucleotide III acting as primer. The ends of the double-stranded cDNA were repaired using T4-DNA polymerase (P-L Biochemicals) by the method of Toole et al., Nature 312 (1984) 342-347.

After attachment of Hind III linkers of the formula IV

(BRL), which had been reacted with polynucleotide kinase and .gamma.-.sup.32 P-labeled ATP, and after cleavage with Hind III, the cDNA was ligated into the vector pAT 153 (A. J. Twigg and D. Sherratt, Nature 283 (1980) 216-218) which had previously been treated with Hind III and alkaline phosphatase from calf intestines (Boehringer Mannheim). The transformation of E. coli HB 101, the amplification with chloramphenicol, and the lysis of the colonies were carried out as above.

The in situ colony hybridization was carried out as above the hybridization probe which was used being a 788 bp DNA fragment which was cut out of the plasmid pL 10/2 using the restriction enzyme Acc I and was labeled to a specific radioactivity of at least 10.sup.8 cpm/.mu.g by nick translation (Maniatis et al., loc. cit.). The filters were washed as follows, for 15 minutes in each case:

in 6.times.SSC at room temperature

in 2.times.SSC at 42.degree. C.

in 1.times.SSC at 50.degree. C.

in 0.1.times.SSC at 50.degree. C.

1.times.SSC=0.15M NaCl,

15 mM sodium citrate, pH 7.0.

2 strongly hybridizing clones were identified by screening. One of the clones (pH 14) contained an insert comprising about 1,060 bp of human DNA. The nucleotide sequence of this cDNA insert was determined by the method of Maxam and Gilbert, loc. cit.

By comparison of the cDNA sequences of the clones pH 14 and pL 10/2 it was found that pH 14 contains the 5'-terminal prolongation of pL 10/2 downstream of an overlap of about 480 bp (figure). pH 14 contains nucleotides 1-1062 of DNA sequence I.

The plasmid pH 14 is cut with Hind III and, partially, with BamHI, and the 841 bp Hind III-BamHI fragment is isolated after electrophoresis on a 1.4% agarose gel (low gel temperature agarose, BIO-RAD).

The plasmid pL 10/2 is cut with Hind III and BamHI, and the 4 kb Hind III-BamHI fragment is ligated with the 841 bp fragment from plasmid pH 14. This construct (plasmid phLS2) codes for a proteinase inhibitor which is prolonged by 9 amino acids at the N-terminal end. This expression plasmid permits, after transformation into E. coli and induction with isopropyl .beta.-D-thiogalactopyranoside, the synthesis of the prolonged proteinase inhibitor, with control by the lac promotor-operator system. ##STR2##