Primary structure of equine growth hormone

Effect of exercise, training, circadian rhythm, age, and sex on insulin-like growth factor-1 in the horse1

Insulin-like growth factor-1 could be a useful marker in the horse for diagnostic, selection, or forensic purposes, provided its physiological regulation is well understood. The objective of this study was to investigate factors, such as acute exercise, fitness training, time of day, sex, and age, that may influence serum IGF-1 in normal, healthy horses. Throughout a 9-wk training program, 6 geldings maintained a mean (+/- SEM) IGF-1 concentration of 302 +/- 29 ng/mL. Moderate or high intensity exercise had no effect on IGF-1 concentrations, when pre- and postexercise values were compared. Over a 24-h period, there was some variation in IGF-1 concentrations but no clear diurnal rhythm. Concentrations of IGF-1 were measured in a large population of thoroughbred horses (1,880) on 3 continents. The population deviated slightly from a normal distribution (P < 0.001) because of large IGF-1 concentrations in 10 horses. The global mean IGF-1 concentration was 310 +/- 2.2 ng/mL, with a greater mean value (P < 0.001) in gonad-intact males (336 +/- 5.6 ng/mL) than in females (303 +/- 3.2 ng/mL) or geldings (302 +/- 3.2 ng/mL). However, the greatest IGF-1 concentrations observed for all stallions, mares, and geldings were 627, 676, and 709 ng/mL, respectively. In mares and geldings, IGF-1 concentrations showed a gradual decrease with advancing age (P < 0.001), but the effect was much less marked in stallions. This study confirms that IGF-1 concentrations are stable, compared with GH concentrations, in the horse and that a meaningful measure of IGF-1 status can be obtained from a daily serum sample.

Oxidation of methionine residues in equine growth hormone by Chloramine-T

1. Reactivity of methionine residues towards Chloramine-T was studied in the equine growth hormone. 2. With a 20.0-fold molar excess of reagent over methionine, full oxidation of the four residues of the protein is achieved. 3. Methionine 4 is the most reactive group, followed by methionines 72 and 178--methionine 123 being the less reactive residue. 4. As judged by circular dichroism spectra and binding assays, protein conformation and binding capacity to specific receptors remains unchanged even after full oxidation of all four methionine residues. 5. Results agree with data previously obtained with bovine growth hormone.

Purification, partial characterization, and radioimmunoassay of prolactin and growth hormone from the Bennett's wallaby

Bennett's wallaby prolactin (wPRL) and growth hormone (wGH) were purified from an aqueous extract of pituitary glands. The extract from 202 glands (6.5 g wet wt) was processed by gel filtration on Sephadex G-100, gel filtration on Sephadex G-100 SF, and then anion-exchange chromatography on DEAE-Sepharose CL-6B. The yields of wPRL and wGH were 5.2 and 15.7 mg, respectively. Since recovery of wPRL from the anion exchange column was 10%, anion exchange was performed in the presence of 20% acetonitrile in a subsequent purification. Recovery from this column was markedly increased to 42%. The purified hormones each gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular weight under reducing conditions of 21,000 and 23,000 for GH and PRL, respectively. Each hormone was positively identified by its N-terminal amino acid sequence, which showed high sequence identity with the equivalent eutherian hormone. Semianalytical gel filtration of purified hormone was used to demonstrate that each hormone remained as a monomer in aqueous solution. Each purified hormone was tested in the heterologous PRL radioimmunoassay (RIA) which has been used in many earlier studies to measure marsupial PRL. Highly purified wPRL was less potent than ovine prolactin (5.3 compared with 1.5 ng/ml at 50% displacement) and the cross-reaction of wGH was < 0.01%. Antibodies were raised against wPRL and wGH and a homologous RIA was developed for each hormone. The sensitivity of the wPRL assay was 0.8 ng/ml which is similar to that of the heterologous PRL assay. Cross-reaction with a number of eutherian pituitary hormones or wGH was < 0.07%. The wGH assay detected 0.8 ng/ml which is similar to that of the heterologous PRL assay. Cross-reaction with a number of eutherian pituitary hormones or wGH was < 0.07%. The wGH assay detected 0.8 ng/ml, cross-reacted with GH from several eutherian species, and showed low cross-reaction with wPRL (< 0.5). In both the wPRL and wGH assays, pituitary homogenates from several species of marsupial diluted in parallel with the wallaby standard, suggesting that these assays will be of use in studies of a number of marsupial species.

An equine growth hormone molecular species lacking the 76-92 peptidic fragment

A new eGH molecular species was isolated and purified by reverse phase HPLC. SDS-polyacrylamide gel electrophoresis, amino acid composition, and C- and N-terminal determinations support a primary structure identical to that described by Zakin et al. (1976), except for the lack of the 76-92 peptidic fragment and the maintaining of 30% of its biological activity.

Primary structure of alpaca growth hormone

Reduced and carbamidomethylated alpaca growth hormone was submitted to tryptic digestion. Peptides in the mixture were purified by reverse phase HPLC and N-terminal determination and an amino acid analysis of each was performed. Data obtained and the already known primary structure of the equine growth hormone allowed the assembly-by homology-of a definite sequence of amino acids for the polypeptide chain of the protein. Present data provide further information about the relationship between growth factors.

Nucleotide sequence of the complementary DNA for turkey growth hormone

Near-full length complementary DNA (cDNA) clones encoding turkey growth hormone (GH) have been isolated from a pituitary library. The longer of the two turkey GH cDNA clones that were sequenced is 803 base pairs (bp) in length and contains 41 nucleotides of the 5'-untranslated region (UTR), an open reading frame of 648 bp that encodes a 25 amino acid leader polypeptide segment as well as a 191 amino acid mature turkey GH protein, and a 3'-UTR that is 92 bp long followed by a 22 bp poly A tract. Comparison of the turkey GH nucleotide sequence to that of other avian GH clones shows the coding region to be greater than 93% homologous while the homology to mammalian GH sequences is between 68 and 78%. Northern blot analysis showed an approximate 800 bp turkey GH processed mRNA transcript that hybridized to the turkey GH cDNA probe. A large up-regulation of turkey GH transcription occurred when intact cultured pituitaries were treated with 1 nM human growth hormone releasing hormone but only modest changes were observed when cultures were treated with thyroid releasing hormone or somatostatin.

Equine growth hormone. Detection of immunoreactive sequences using poly- and monoclonal antibodies

The immunochemical behavior of several fragments of equine growth hormone (eGH) was examined using competitive binding assays with antibodies (Abs) to eGH obtained from different sources. Antigenicity was detected within the sequences 5-72 and 73-123 by rabbit Abs to eGH and by three mouse monoclonal antibodies (MAbs) produced by using bovine growth hormone as immunogen, but showing heteroclitic properties towards eGH. The polyclonal Abs to eGH also recognized as immunoreactive two smaller peptides corresponding to the amino acid residues 52-72 and 110-123. By contrast, the heteroclitic Abs to eGH developed by hypopituitary patients therapeutically injected with human growth hormone failed to react with any eGH-derived fragment. The rabbit polyclonal Abs and the mouse MAbs scarely discriminated between native and S-carbamidomethylated eGH, while the heteroclitic human Abs detected a clear difference between the native and the modified hormone.

Conformational comparison in the growth hormone family

1. The method of Kubota et al. [Biochim. biophys. Acta 701, 242-252 (1982)] was applied to several members of the growth hormone family in order to examine their conformational homology. 2. The method neither detects differences between rat, cow, sheep, horse and alpaca hormones, nor between monkey and human hormones. 3. Lack of homology between primate and non-primate growth hormones was found in segments 42-49 and 184-191. The first fragment could be linked to species-specificity.

The complete amino acid sequence of growth hormone from the sea turtle (Chelonia mydas)

The complete amino acid sequence of growth hormone (GH) from a reptilian species (the sea turtle, Chelonia mydas) has been determined for the first time. The hormone was reduced, carboxymethylated, and subsequently cleaved in turn with cyanogen bromide and Staphylococcus aureus protease. The intact protein was also cleaved with lysyl endopeptidase and o-iodosobenzoic acid. The resulting fragments were exclusively separated by reversed-phase high-performance liquid chromatography and subjected to sequence analysis by automated gas-phase sequencer employing the Edman method. The sea turtle GH consist of 190 amino acid residues with two disulfide linkages formed between residues 52-160 and 180-188, and possesses a microheterogeneity, indicated by the presence or absence of an additional alanine residue at the N-terminus. Sequence identities of sea turtle GH to other species of GH are 89% with chicken GH, 79% with rat GH, 68% with blue shark GH, 58% with eel GH, 59% with human GH, and 40% with a teleostean GH such as chum salmon. On the basis of amino acid sequence comparisons, a molecular phylogenetic tree is proposed.

Secondary structure prediction of 11 mammalian growth hormones

The secondary structure of 11 mammalian growth hormones has been predicted by combining five different methods. Three long helical regions located around residues 20, 120, and 170 constitute the most prominent common feature in the species studied. The strong amphiphilic character of these helices suggests that they can play an important role in protein folding or stability.

Ethoxyformylation of histidine residues in equine growth hormone

Reactivity of histidine residues in equine growth hormone to ethoxyformic anhydride was studied. The existence of two kinetically different sets was demonstrated: one of them including only the slow reacting histidine 169 (k = 0.164 min-1) and the other containing fast reacting histidines 19 and 21 (k = 0.892 min-1). A correlation between the decrease in the capacity to compete with 125I-labeled hormone for rat liver binding sites and the degree of ethoxyformylation of the fast group was found. Circular dichroism studies indicated no significant conformational changes in the protein with all three residues modified. These results fully agree with those obtained for bovine growth hormone which is further evidence supporting the vinculation of histidines 19 and/or 21 with the binding site of these hormones to their specific receptors.

Three-dimensional structure of a genetically engineered variant of porcine growth hormone

The three-dimensional structure of a genetically engineered variant of porcine growth hormone, methionyl porcine somatotropin (MPS), has been determined at 2.8-A resolution, using single crystal x-ray diffraction techniques. Phases were obtained by use of a single isomorphous K2OsCl6 derivative and were improved by use of the density modification procedure. The MPS structure is predominantly helical. It consists mainly of four antiparallel alpha-helices arranged in a left twisted helical bundle, a structural motif observed in a number of other unrelated proteins. However, the way the four helices are connected in the bundle is unusual and, to our knowledge, has never been reported before. Alignment of the amino acid sequence of MPS with that of other growth hormones reveals that residues within the alpha-helices are predominantly invariant and thus these invariant residues are necessary to maintain the structural integrity of these proteins.

Internal homologies in the two aspartokinase-homoserine dehydrogenases of Escherichia coli K-12

In Escherichia coli, AK I- HDH I and AK II- HDH II are two bifunctional proteins, derived from a common ancestor, that catalyze the first and third reactions of the common pathway leading to threonine and methionine. An extensive amino acid sequence comparison of both molecules reveals two main features on each of them: (i) two segments, each of about 130 amino acids, covering the first one-third of the polypeptide chain, are similar to each other and (ii) two segments, each of about 250 amino acids and covering the COOH-terminal 500 amino acids also present a significant homology. These findings suggest that these two regions may have evolved independently of each other by a process of gene duplication and fusion previous to the appearance of an ancestral aspartokinase-homoserine dehydrogenase molecule.

Complete amino acid sequence of mouse prolactin

The complete primary structure of mouse prolactin has been established on the basis of tryptic peptides from cyanogen-bromide-treated, S-carboxymethylated mouse prolactin and Staphylococcus-aureus-protease-cleaved overlaps, which were sequenced by manual liquid-phase and solid-phase Edman degradation. Three disulfide bonds were assigned to Cys-4-Cys-9, Cys-56-Cys-172, and Cys-189-Cys-197 by digestion of intact prolactin with S. aureus protease. One of the characteristics to date is replacement of Trp-89, which is commonly present among prolactin, growth hormone and choriomammotropin, by serine. It was suggested, by comparison with five other prolactins, five growth hormones and human choriomammotropin, that Asp-18, His-25, Ser-60 and Thr-63 are essential to lactogenic activity.

Studies on prolactin 48: isolation and properties of the hormone from horse pituitary glands

Isolation of prolactin from equine pituitary glands has been described. It has a potency of 42 IU/mg in the pigeon crop-sac test and consists of 199 amino acids. The hormone has only four half-cystine residues in contrast to other mammalian prolactins which have six residues. From NH2-terminal sequence analysis and amino acid composition of cyanogen bromide fragments, the NH2-terminal disulfide loop is missing in the equine prolactin molecule. Circular dichroism spectra indicate that the alpha-helical content of equine prolactin appears to be lower (50%) than that found in the ovine hormone (65%).

Primary structure of seiwhale pituitary somatotropin

Seiwhale somatotropin has been isolated from seiwhale pituitaries. It was cleaved by cyanogen bromide, trypsin and chymotrypsin. The peptide fragments were separated and purified by gel filtration on Sephadexes, ion exchange chromatography, high voltage electrophoresis and paper chromatography. Amino acid sequences of the isolated peptides were studied by the dansyl-Edman procedure. The data obtained suggested a primary structure of seiwhale somatotropin consisting of 190 amino acid residues and showed a high degree of homology with somatotropins of many other species.

Immunological properties of two related fragments from human and equine growth hormones

The immunological properties of a synthetic human growth hormone fragment comprising the amino acids 73 through 128 and of the homologous natural horse growth fragment formed by amino acids 73 through 123, have been comparatively studied. Antisera obtained in rabbits inoculated with the native human hormone or with the fragments, were used. By hemagglutination experiments both fragments have the same reactivity toward the anti-human growth hormone serum, but complement fixation curves detect the existence of at least two populations of antibodies presumably originated against the sequence 73-128 of human growth hormone. Of these, only one of the corresponding antigenic areas is present in the homologous region of equine growth hormone. The known cross-reactivity detected between both hormones is thus partially explained.