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C Schwabe

Publications and source records attributed to C Schwabe.

At least 37 records · Page 2Linked to original sources
PubMed1996

Introduction of relaxin properties into other hormones of insulin-like structure.

Sequence comparison of natural relaxins and the investigation of the structure function relationship of chemically synthesized relaxin analogs have been used to identify two arginine residues on the surface of the main helix of the B chain as hormone-receptor interaction site. This site is sensitive to structural changes, in particular the conformation of the A chain loop. Introducing the active site of relaxin into noncrossreacting structural analogs such as insulin and bombyxin required a four amino acid exchange. Both hybrid hormones bound to the anti-porcine relaxin antibody R6 with high affinity, and the insulin analog, with an additional C-terminal truncation of the B chain, crossreacted with rat relaxin-receptors.

Amino Acid Sequence↗
PubMed1995

A novel Leydig cell cDNA-derived protein is a relaxin-like factor.

According to Burkhardt et al. (Burkhardt, E., Adham, I. M., Brosig, B., Gastmann, A., Mattei, M. G., and Engel, W. (1994) Genomics 20, 13-19) Leydig cells contain the message for a protein of the insulin/relaxin family which was named Leydig cell insulin-like protein (LEY I-L). We have synthesized the human LEY I-L according to the amino acid sequence deduced from the published cDNA structure and obtained preliminary results concerning its potential target organs and its biological activity. Leydig cell insulin-like protein binds specifically to crude membrane preparations of mouse uterus and brain and shows cross-reactivity with the relaxin receptor, but not the insulin receptor. On the basis of these observations, together with the results of earlier structure-function considerations, we suggest that the new protein is a relaxin-like factor. By itself the new factor shows no obvious effect, but when given together with relaxin it significantly enhances relaxin-mediated widening of the mouse symphysis pubis.

Amino Acid Sequence↗
PubMed1994

Functional importance of the A chain loop in relaxin and insulin.

Relaxin and insulin are disulfide homologues with divergent functions and antigenicity. We have synthesized human relaxin II and porcine insulin and several A chain loop variants of each and measured the effect of substitutions in vivo and in vitro. Substitution of IleA10 in insulin with glycine reduced the receptor binding ability by 2 orders of magnitude. Conversely, exchange of the glycine A14 residue in relaxin, which corresponds to the insulin position A10 for isoleucine, reduced the bio-activity and the receptor binding capacity of relaxin about 100-fold. Substitution of L-Ala in insulin as well as relaxin represented a compromise that allowed both hormones to recover about 30% of the native potency. X-ray analysis and computer-derived energy calculation confirm our receptor binding and biological potency studies, which suggest that the functional difference between derivatives and native hormones is based upon a structural change introduced into the A chain loop by substitution of the penultimate intrachain loop residue. In order to achieve a conformation that favors dynamic or passive interaction with the receptor, insulin and relaxin require a different A chain loop structure in spite of the striking overall similarity.

Animals↗
PubMed1994

Relaxin: structures, functions, promises, and nonevolution.

During the last two decades synthetic chemistry and molecular biology have transformed the little-known parturition-mediating factor relaxin into a chemically defined entity. Relaxin is a disulfide bond analog of insulin that shows no cross-reactivity to the insulin receptors, causes widening of the birth canal in most mammals, and has additional or different functions in various species. The receptor interaction site in relaxin has been located quite precisely in the midregion of the B chain helix and is now known to involve two arginine residues that project from the alpha helix in an n, n + 4 configuration. The A chain of relaxin which appears to be uninvolved in receptor binding, is nonetheless essential. In fact, a major structural determinant in relaxin and insulin responsible for achieving either an insulin-like or a relaxin-like conformation is located in the penultimate position in the intrachain loop of the A chains.

Amino Acid Sequence↗
PubMed1993

Mouse relaxin: synthesis and biological activity of the first relaxin with an unusual crosslinking pattern.

According to a recently published cDNA sequence, mouse relaxin has an extra amino acid in the C-terminal end of the A chain and thus an interchain loop consisting of 25 amino acids instead of the usual 24-membered ring. Because of the restrictive disulfide link arrangement the extra residue can be expected to cause a loop out in the C-terminal alpha-helix. We have chemically synthesized authentic mouse relaxin as well as an analog without the additional A chain residue and found that the native hormone, although active, was inferior to its insulin-like analog. This result is in harmony with our previous study which suggests that the surface of relaxin represented by the C-terminal helix of the A chain is positioned opposite to the surface that contains the receptor interaction site and therefore is less sensitive to modifications.

Amino Acid Sequence↗
PubMed1993

The expression of human relaxin in yeast.

The chemically synthesized DNA-coding sequence for an artificial single chain human relaxin consisting of a B chain, an Arg-Arg-Glu-Phe-Lys-Arg-connecting peptide, followed by the A chain, was used to construct two plasmids which were introduced into Saccharomyces cerevisiae. Expression of the relaxin-coding sequence was under the control of either the yeast TDH3 promoter or the CUP1 promoter. The yeast alpha-factor signal sequence was used to direct the protein into the secretory path, and the appearance of human relaxin in the growth medium was confirmed by radioimmunoassay and immunoblotting. Partially purified human relaxin from yeast was biologically active in the mouse symphysis pubis assay and radioreceptor assay.

Amino Acid Sequence↗
PubMed1993

Attenuation of antepartum relaxin surge and induction of parturition by antiprogesterone RU 486 in sheep.

Pregnant ewes were injected with either the antiprogesterone, RU 486 (4 mg kg-1 body weight, i.m.; n = 5), 3000 iu relaxin (i.m.; n = 9), or diluent (n = 8) at 12:00 h on days 144 and 145, to determine its effect on progesterone and relaxin secretion, and on induction of lambing. RU 486 induced earlier lambing (P < 0.01) compared with diluent treatment, but relaxin treatment did not significantly reduce the interval to parturition. Mean injection-lambing intervals were 31 +/- 2, 109 +/- 23 and 121 +/- 27 h for the RU 486, relaxin and diluent groups, respectively. There was no incidence of difficult birth (dystocia); all lambs were vigorous at birth; and placenta delivery was rapid (within 207 min) with RU 486 and relaxin treatments compared with diluent treated controls. Plasma progesterone concentrations averaged 11 ng ml-1 during the pretreatment period for all animals. RU 486 had a biphasic effect on progesterone concentrations, causing an initial increase (P < 0.05) within 2 h, and then an abrupt drop (P < 0.01) to 6 ng ml-1 by 18:00 h on day 145. Progesterone concentrations remained consistently lower (P < 0.05) in relaxin-treated ewes than in diluent-treated controls from days 144 to 147 and then began a steady decrease to 4 ng ml-1 on the day of parturition (days 149 and 150) in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The receptor-binding site of human relaxin II. A dual prong-binding mechanism.

Recent structure/function studies on human relaxin II have led to the conclusion that the arginines B13 and/or B17 are important for biological activity. These studies have been confirmed and extended with the help of chemically synthesized derivatives, i.e. dicitrulline (B13, B17), two monocitrulline (B13 and B17), a dilysine (B13, 17), and alanine (B17) relaxins. The CD spectra of synthetic human relaxin and of the derivatives are indistinguishable. Yet, only the native human relaxin II is biologically active and binds strongly to relaxin receptor preparations in vitro. The inactivation is strictly due to side chain functions, in particular the replacement of either or both arginines in the positions B13 or B17. Binding is mediated by a two-prong electrostatic and hydrogen-binding interaction via arginines B13 and B17. Neither B13 nor B17 alone are sufficient and a positive charge equidistant from the B chain helix is equally insufficient. This binding mechanism appears to be unique, as concerns hormone receptor interaction.

Amino Acid Sequence↗
PubMed1992

Relaxin receptors in mice: demonstration of ligand binding in symphyseal tissues and uterine membrane fragments.

A monocomponent, high specific activity, carrier-free porcine relaxin tracer (125I) has made it possible for us to demonstrate relaxin receptors in the symphysis pubis, uterus, and ovary via autoradiography. The receptors are concentrated in the symphyseal ligament and the peripheral layers of uterus and ovary. Specific relaxin binding was observed in crude membrane preparations of uteri, ovaries, and brain, whereas crude membranes of leg muscle and kidney showed only nonspecific binding. Uterine membranes prepared from estrogen-primed mice showed tracer binding, which could be significantly inhibited by porcine relaxin in a dose-dependent manner, but not by insulin. A linear Scatchard plot suggested the presence of only one kind of receptor and a dissociation constant of 5 x 10(-10) M, which is commensurate with an electrostatic double ion pair binding mechanism.

Animals↗
PubMed1991

Total synthesis of human relaxin and human relaxin derivatives by solid-phase peptide synthesis and site-directed chain combination.

Human relaxin, a two-chain protein hormone, was synthesized by solid-phase peptide synthesis in combination with a novel thiol-protecting group strategy whereby the three disulfide bonds could be synthesized sequentially and without error. The final product was shown to be homogeneous by reversed-phase high performance liquid chromatography and electrophoresis and had the correct amino acid composition and sequence. Tryptic digestion and peptide mapping of the synthetic relaxin by reversed-phase high performance liquid chromatography resulted in a pattern identical with that produced by standard tryptic relaxin fragments synthetized by different methods. Three human relaxin derivatives containing oxidized methionine, formyltryptophan, and bis[B13,B17-citrulline]-relaxin, were produced and their biological activity and structural similarity to human relaxin was assessed. All derivatives, except those containing modified tryptophan residues, showed indistinguishable circular dichroic spectra, indicating that the modifications did not cause significant structural changes. However, only human relaxin and the tryptophan- and methionine-protected relaxin derivatives showed bioactivity. The derivative in which the two arginines in positions B13 and B17 had been replaced by the uncharged isosteric amino acid citrulline were biologically inactive. This observation confirms preliminary studies (Büllesbach, E. E. and Schwabe, C. (1988) Int. J. Pept. Protein Res. 32, 361-367) that suggested that these two conserved arginines located in the midregion of the relaxin B chain are essential for the function of the hormone.

Amino Acid Sequence↗
PubMed1991

Antiprogesterone, RU 486, facilitates parturition in cattle.

RU 486, a potent progesterone antagonist with high affinity for progesterone receptor, was used alone or in combination with relaxin in late pregnant cattle to determine its effect on induction of parturition. Cross-bred beef cattle were bred by artificial insemination. An indwelling cannula was inserted into a jugular vein on day 269 (expected term = day 283) for repeated blood sample collection. On day 277, the cattle were assigned randomly to three groups (n = 6 each): group 1 received RU 486 (2 mg/kg BW, im) at 0800 h on days 277 and 278; group 2 received the same RU 486 treatment plus 3000 U relaxin, injected sc at 0800 h on day 278; and group 3 served as controls and received vehicle injection. Parturition occurred 55 h after treatment in group 1 and 53 h after treatment in group 2 compared with 210 h in the controls (P less than 0.01). The calves from treated groups were vigorous at birth, and their birth weights (32 and 33 kg in groups 1 and 2) were less than those of control calves (38 kg; P less than 0.01). There was no incidence of difficult birth (dystocia) with RU 486 treatment compared with that in the controls. Placenta delivery averaged 6.5 h after birth in both RU 486-treated groups and did not differ from the control value (5 h). Plasma progesterone concentrations averaged 8.2 ng/ml during the pretreatment period for all animals. Progesterone started to decrease markedly by 1200 h on day 278, dropped to about 4 ng/ml by 2400 h that same day, and was at basal levels on day 279, the day of calving, in two hormone-treated groups. In sharp contrast, progesterone was maintained at about 6 ng/ml in placebo-treated controls during this period and did not decrease to basal levels until 2 days before parturition on day 286 (P less than 0.01). Peak RU 486 in plasma was 7.2 ng/ml after the first injection and 14.3 ng/ml after the second injection, and averaged 7.9 ng/ml on the day of induced calving (day 279). Peak relaxin was 4.1 ng/ml after hormone injection. The results indicate that RU 486 alone or combined with relaxin precisely controlled the time of parturition in cattle in late pregnancy. Such treatment can be used to facilitate parturition and increase survival rates of neonatal calves without detrimental effects of dystocia, retention of placenta, and delayed postpartum fertility.

Animals↗
PubMed1991

Effect of relaxin on facilitation of parturition in dairy heifers.

Purified pig relaxin (3000 U/mg) was injected i.m. into pregnant Holstein dairy heifers on Day 276 or 277 to determine its effect on parturition and sequential measurements of the pelvic area, cervical dilatation, and peripheral blood-plasma concentrations of progesterone and relaxin. Treatments included phosphate-buffer saline (2 ml, Group C, N = 7), relaxin once (1 mg, Group 1R, N = 7), and twice (2 mg, 12 h apart; Group 2R, N = 7). Intervals (mean +/- s.e.) between the first injection of relaxin or PBS and calving were 64 +/- 17, 80 +/- 19 and 125 +/- 34 h for Groups 2R, 1R and C, respectively. The calving intervals were reduced in Groups 2R (P less than 0.01) and 1R (P less than 0.05) compared with Group C. The incidence of dystocia was 29% (2 of 7) in Group 2R and 43% (3 of 7) in Group 1R compared with 57% (4 of 7) in Group C (P less than 0.01). Body weights and ratios of males to females of the calves were similar (P greater than 0.05) between groups. Progesterone plasma concentrations decreased (P less than 0.01) earlier in Groups 1R and 2R compared with Group C, and this acute decrease began within 6 h of treatment. At 24 h after relaxin or PBS injection, progesterone concentrations were 2.7 +/- 1.1 ng/ml for Group 2R, 3.5 +/- 0.9 ng/ml for Group 1R, and 6.0 +/- 0.1 ng/ml for Group C. Relaxin reached peak blood-plasma levels of 19 +/- 2.2 ng/ml 1 h after injection of relaxin, but remained unchanged, 0.3 +/- 0.01 ng/ml, in Group C. Pelvic area was increased 26%, 22% and 14% and cervical dilatation was increased 109%, 76% and 53% 48 h after injection in Groups 2R, 1R and C, respectively, but these responses were similar among groups at the time of parturition. We conclude that two i.m. injections of relaxin facilitated earlier calving, acutely decreased progesterone secretion, increased cervical dilatation and pelvic area expansion, and decreased the incidence of dystocia in dairy heifers.

Animals↗
PubMed1991

Purification from human pregnancy serum of a low molecular weight mitogen similar to placental lactogen and growth hormone.

Recently, we isolated from the serum of pregnant women a factor that induced rapid proliferation of a lactogen-dependent rat lymphoma cell line (Nb2). This mitogenic factor is reasonably specific to pregnancy, since it was present in serum samples from second trimester as well as term-pregnant women, but not in those of adult men or cycling females. It is unlikely that this mitogenic activity (referred to as pregnancy mitogen [PM]) is due to contamination by classical lactogens, since acetone fractionation of serum yielded a preparation devoid of placental lactogen and prolactin, as determined by radioimmunoassays. Further purification of acetone precipitates from term-pregnant serum by ion exchange chromatography and gel filtration yielded a mitogenic activity with a relative mol wt of approximately 10,000. PM activity in the NB2 cell bioassay was not affected by the presence of prolactin antiserum. However, its activity was immunoneutralized by coincubation with anti-placental lactogen serum and, to a lesser extent, anti-growth hormone serum. It appears that PM was not generated by our extraction procedure, since gel filtration of whole serum also yielded a bioactive fraction of approximately 10 kDa. PM was further purified to homogeneity by high-performance liquid chromatography. Examination of the preliminary amino acid composition of PM revealed differences from that of a bioactive fragment of growth hormone and a corresponding portion of placental lactogen, suggesting that PM could be either a molecular variant of these hormones or a novel protein.

Amino Acids↗
PubMed1990

Livedo racemosa generalisata: an evaluation of thirty-four cases.

The results of investigations in 34 patients (28 women, 6 men) with livedo racemosa generalisata are presented. Neurologic or psychiatric symptoms were present in 28 patients. Nineteen patients had had one or more cerebral infarctions, and epilepsy (Sneddon's syndrome) developed in six. In most cases livedo preceded the neurologic disorder. In addition, many patients with livedo racemosa generalisata had Raynaud's phenomenon, cardiac abnormalities, or vascular changes in the ocular fundus.

Adult↗
PubMed1990

New thoughts on the evolution of hormone-receptor systems.

A possible pathway of the evolution of hormone-receptor systems has been discussed in light of the genomic potential hypothesis. Unlike the Darwinian system which is based on uninvestigatable chance events, the genomic potential hypothesis offers predictions based upon chemical determinism (boundary determinism). Accordingly, the production of highly specific protein-protein interactions between receptors and hormones, for example, are based upon the development of interacting components before the primordial chemistry was segregated by membranes. It is proposed that in addition to the primary structure (coding activity) a higher level of information exists in the genome which caused genomic products to function in a complementary fashion in living systems. The first steps in that direction have already been taken via experiments on sense and antisense peptides which may have specific relationships to each other. It is clear that I have not given an answer but I hope that I have touched upon certain aspects of a problem that can be illuminated better by a new and different approach to evolution. The hormone-receptor development was probably a powerful formative force in the development of macroorganisms, and its baffling complexity can only begin to find an explanation on the basis of structure/function relationships of the encoding material and its products.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Relaxin.

1. Relaxin is a hormone of reproduction that appears to affect parturition, uterine accommodation, and sperm motility to varying degrees in many species. 2. All relaxins have the same two chain, disulfide-linked insulin-like structure and two arginine residues in the midregion of the B chain. 3. The active relaxin molecule is produced by excision of a connecting peptide from the prohormone. 4. The biosynthetic pathways of insulin and relaxin are alike, but the relaxin prohormone is about twice as large as the corresponding proinsulin. 5. The primary structures of relaxins from apparently closely related species differ significantly in their amino acid compositions and do not fit into the traditional scheme of molecular evolution.

Amino Acid Sequence↗