Characterization of human growth hormone from acromegalic pituitary tumors

Human growth hormone (HGH) was extracted from acromegalic pituitary tumors at pH 10.5 and precipitated with ammonium sulfate at 20-40% saturation. It was purified on a Sephadex G-100 column to yield monomeric HGH. The tumor-HGH was indistinguishable from the authentic one in polyacrylamide gel electrophoresis at pH 8.3 or in the presence of sodium dodecyl sulfate, high-performance liquid chromatography, radioimmunoassay, peptide map, amino acid composition and N-terminal partial amino acid sequence. The tumor-HGH is active in the tibia assay and bodyweight gain test in hypophysectomized rats with comparable potency to that of the authentic sample.     

Luteinizing hormone of the sperm whale. Isolation, separation into subunits and study of the amino acid sequence of the alpha-subunit

The luteinizing hormone isolated from sperm-whale pituitary was separated into two subunits, alpha- and beta-, by ion-exchange chromatography on sulfoethyl-Sephadex. The hormone subunits were reconstituted, carboxymethylated and cleaved by BrCN and proteolytic enzymes. In order to block tryptic hydrolysis at lysine residues the alpha-subunit was subjected to maleylation. Large-sized fragments of BrCN were cleaved by chymotrypsin and trypsin, while large-sized fragments of trypsin were split by chymotrypsin. The resulting peptides were separated by gel filtration on Sephadex, ion-exchange chromatography on Aminex A-5 and thin-layer partition chromatography on cellulose. The amino acid sequence of the peptides was determined by the Edman method, using identification of the N-terminal amino acids in a reaction with dansyl chloride or dimethylaminoazobenzene-4-isothiocyanate. It was shown that the alpha-subunit of the luteinizing hormone is a peptide chain consisting of 96 amino acid residues with covalently linked carbon chains at asparagine residues at positions 56 and 82. The N-terminal amino acid of the alpha-subunit is phenylalanine, the C-terminal amino acid is serine. The alpha-subunit is heterogeneous at the N-end, i. e. beside phenylalanine it contains threonine and trace amounts of proline, aspartate, glutamate and glycine.     

Snake venomics: characterization of protein families in Sistrurus barbouri venom by cysteine mapping, N-terminal sequencing, and tandem mass spectrometry analysis

The protein composition of the crude venom of Sistrurus barbouri was analyzed by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. Proteins were separated by reversed phase high-performance liquid chromatography and characterized by N-terminal sequence analysis. The molecular mass and number of cysteine residues of the purified proteins were determined by matrix-associated laser desorption/ionization-time of flight mass spectrometry. Selected protein bands were subjected to in-gel tryptic digestion and peptide mass fingerprinting. Analysis of the tandem mass spectrometry spectra of selected doubly-charged peptide ions was done by collision-induced dissociation in a quadrupole-linear ion trap instrument. Our results show that the venom proteome of the pigmy rattlesnake S. barbouri is composed of proteins belonging to a few protein families, which can be structurally characterized by their disulfide bond contents.     

Analysis of lysine-rich histones from the unicellular green alga Chlamydomonas reinhardtii

The H1 histones of the unicellular green alga Chlamydomonas reinhardtii were extracted from isolated nuclei, fractionated by high performance liquid chromatography, and analyzed by two-dimensional electrophoresis, peptide mapping, and N-terminal sequencing. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of 5% perchloric acid extracts of isolated C. reinhardtii nuclei revealed two H1 proteins (H1A and H1B). Two-dimensional gel analysis did not reveal heterogeneity of either algal H1 protein, but did detect differences in the hydrophobic amino acid content of the C. reinhardtii H1A and H1B. Digestion of H1A and H1B with V8 protease revealed two distinctly different peptide maps. C. reinhardtii H1 peptide maps were not at all similar to those of Pisum H1, but algal and pea H2B peptide maps did show some peptides in common. Seventeen amino acid residues were obtained from C. reinhardtii H1A amino terminal sequencing, while the H1B N-terminus was blocked. A search of protein data bases revealed no sequence homology of the H1A N-terminus with any known protein. Chlamydomonas histones fractionated by high performance liquid chromatography revealed minor components (histone variants) for H2A and H2B. The amino acid composition of Chlamydomonas lysine-rich histones was compared to those of various other unicellular algae.     

Recombinant-DNA-derived bovine growth hormone from Escherichia coli. 2. Biochemical, biophysical, immunological and biological comparison with the pituitary hormone

Bacterially synthesized, recombinant-DNA-derived bovine growth hormone (r-bGH), prepared as described in the preceding paper in this journal, has been characterized in comparison with pituitary bovine growth hormone (pit-bGH). The characterization criteria include sodium dodecyl sulfate/polyacrylamide gel electrophoresis, automated N-terminal sequence analysis, amino acid composition, isoelectric focusing, reverse-phase high-performance liquid chromatography, ultraviolet absorbance, analysis for free protein thiol, sizing by gel filtration, circular dichroism, radioimmunoassay and biological activity in the hypophysectomized rat weight-gain assay. In every respect the r-bGH appears to be virtually identical to pit-bGH.     

Amino acid sequence of the ribosomal protein HS23 from the halophilicHaloarcula marismortui and homology studies to other ribosomal proteins

The ribosomal protein HS23 from the 30S subunit of the extreme halophilicHaloarcula marismortui, belonging to the group of archaea, was isolated either by RP-HLPLC or two-dimensional polyacrylamide gel electrophoresis. The complete amino acid sequence was determined by automated N-terminal microsequencing. The protein consists of 123 residues with a corresponding molecular mass of 12,552 Da as determined by electrospray mass spectroscopy; the pI is 11.04. Homology studies reveal similarities to the eukaryotic ribosomal protein S8 fromHomo sapiens, Rattus norvegicus, Leishmania major, andSaccharomyces cerevisiae.     

A mycorrhiza-responsive protein in wheat roots

A small protein, designated Myk15, was found to be strongly induced in wheat ( Triticum aestivum) roots colonized by the arbuscular mycorrhizal fungus Glomus intraradices. This protein, which is most abundant in root fractions characterized by strong mycorrhizal colonization, has been characterized using two-dimensional polyacrylamide gel electrophoresis and microsequencing. It has an apparent molecular mass of 15 kDa and an isoelectric point of 4.5. The N-terminal sequence has high similarity to a peptide sequence deduced from an expressed sequence tag (EST) clone derived from Medicago truncatula roots colonized by G. intraradices. This EST clone is predicted to code for a protein with a similar size and isoelectric point as Myk15. The N-terminus of the deduced M. truncatula protein contains a highly hydrophobic stretch of 24 amino acid residues preceding the region with high similarity to the Myk15 N-terminus. This hydrophobic stretch is predicted to form a transmembrane alpha-helix and may correspond to a cleavable targeting domain.     

Amino acid sequence studies on cyanogen bromide peptides of chicken caldesmon which bind to calmodulin

Three major calmodulin-binding cyanogen bromide peptides (fragments A, B, and D) were isolated from chicken gizzard muscle caldesmon and their amino acid sequences were determined. The molecular masses of fragments A, B, and D were estimated to 16, 12, and 9 kDa, respectively, by SDS-urea polyacrylamide gel electrophoresis. Fragment A was composed of 102 amino acid residues and contained homoserine at the C terminus. The amino acid sequence from the 37th residue of fragment A corresponds to the N-terminal sequence of the 15 kDa peptide which was obtained by thrombin digestion [Mornet, D., Audemard, E., & Derancourt, J. (1988) Biochem. Biophys. Res. Commun. 154, 564-571]. Thrombin 15 kDa peptide binds to F-actin but does not bind to calmodulin. Thus the N-terminal 36 residues and the C-terminal part from the 37th residue of fragment A are supposed to bind to calmodulin and F-actin, respectively. The sequences of fragments B and D were identical, but fragment D was composed of 64 amino acid residues and ended with tryptophan, whereas fragment B was of 98 or 99 amino acid residues and ended with proline. Both fragments B and D are supposed to be the C-terminal peptides of chicken caldesmon. Fragment B had heterogeneous sequences at the C-terminal region. These results can explain the reported heterogeneity of chicken caldesmon in charge and molecular mass.     

Purification and characterization of a low and a high molecular weight form of epidermal growth factor from rat urine

Two forms of epidermal growth factor (EGF) have been purified to homogeneity from rat urine by immunoaffinity chromatography and gel filtration. For one of the purified peptides the molecular mass has been determined to be 5891 by mass spectrometry. This peptide consists of 51 amino acid residues. The sequence of the first 48 amino acid residues is identical to the previously published sequence for submandibular rat EGF. The C-terminal three residues (49-51) are Trp-Trp-Lys. The other purified peptide has a molecular mass of 45 kDa as determined by SDS-polyacrylamide gel electrophoresis. The N-terminal sequence is Asn-Tyr-Lys-Asp-(Cys)-Gly-Pro-Gly-Gly-(Cys)-Gly-Ser-His-Ala. Both the high and the low molecular mass form of urinary rat EGF are able to bind to the human placenta receptor for EGF.     

Primary structure of the ovine pituitary follitropin beta-subunit.

The complete amino acids sequence of the ovine pituitary follitropin beta-subunit was established by studying the tryptic, chymotryptic and thermolytic peptides. The N-terminal sequence of the subunit was confirmed by subjecting the oxidated protein to Edman degradation in an automated sequenator. Automated Edman degradation of the reduced and alkylated (with iodo [14C]acetamide) beta-subunit indicated that most of the molecules used in the sequence studies had lost the N-terminal serine residue. This also confirmed the location of the first five half-cystine residues in the sequence. The proposed structure shows the presence of 111 amino acid residues with the two oligosaccharide moieties linked to asparagine residues located at positions 6 and 23. Heterogeneity occurs at both the termini of the polypeptide chain. Comparison of the sequence of beta-subunit of the ovine hormone with that proposed for human follitropin beta-subunit shows the absence of any deletions in the middle of the peptide chain. Of the 13 replacements, 11 residues can be explained on the basis of a single base change in the codon. The single tryptophan residue of the follitropin occupies an identical position in all the four species that have been studied. The region corresponding to residues 63-105 of the ovine beta-subunit is highly conserved in all the species.     

Influence of lipids on membrane assembly and stability of the potassium channel KcsA

A novel antibacterial peptide, moricin, isolated from the silkworm Bombyx mori, consists of 42 amino acids. It is highly basic and the amino acid sequence has no significant similarity to those of other antibacterial peptides. The 20 structures of moricin in methanol have been determined from two-dimensional 1H-nuclear magnetic resonance spectroscopic data. The solution structure reveals an unique structure comprising of a long alpha-helix containing eight turns along nearly the full length of the peptide except for four N-terminal residues and six C-terminal residues. The electrostatic surface map shows that the N-terminal segment of the alpha-helix, residues 5-22, is an amphipathic alpha-helix with a clear separation of hydrophobic and hydrophilic faces, and that the C-terminal segment of the alpha-helix, residues 23-36, is a hydrophobic alpha-helix except for the negatively charged surface at the position of Asp30. The results suggest that the amphipathic N-terminal segment of the alpha-helix is mainly responsible for the increase in permeability of the membrane to kill the bacteria.     

Isolation and purification of the extracellular and intracellular portions of the beta subunit of (Na+,K+)-ATPase.

The beta subunit of lamb kidney (Na+,K+)-ATPase was isolated by size exclusion high performance liquid chromatography. Treatment of the beta subunit with formic acid yielded two peptide fragments which were purified via reversed phase high performance liquid chromatography. These peptides were identified by sodium dodecylsulfate polyacrylamide gel electrophoresis, amino acid analysis and N-terminal sequencing as (Pro 94-Ser 302), a largely hydrophilic peptide which comprises the major portion of the extracellular domain including six Cys residues which participate in disulfide bond formation and three glycosylation sites and a smaller peptide (Ala 1-Asp 93) which contains the single membrane spanning region and the intracellular domain.     

Peptide mapping of protein bands from polyacrylamide gel electrophoresis by chemical cleavage in gel pleces and re-electrophoresis

A simple method has been developed for peptide mapping of protein bands obtained by polyacrylamide gel electrophoresis. The procedure is based on selective acid hydrolysis of aspartyl-prolyl bonds which occur in proteins with an average frequency of 1 per 400 amino acid residues. A gel piece containing the protein to be analyzed is soaked with 75% formie acid. For the subsequent incubation at 37°C for 24 h the gel piece is immersed in liquid paraffin. After removal of formic acid by lyophilization the gel piece is rehydrated in buffer and placed into the sample well of a second polyacrylamide gel on which the generated peptides are electrophoretically separated.     

Effects of a leucine analog on growth hormone processing and secretion by cultured cells

Bovine and rat growth hormones (bGH and rGH, respectively) possess signal peptides that direct the hormone to the secretory pathway and are proteolytically cleaved prior to secretion. Previous in vitro translation studies indicated that incorporation of the polar leucine analog beta-hydroxyleucine into de novo synthesized polypeptides inhibits signal peptide function. To test the effects of this analog on GH secretion by cultured animal cells, transfections of mouse L-cells with a bGH expression plasmid or metabolic labeling of endogenous rGH in anterior pituitary cells was performed in the absence or presence of beta-hydroxyleucine. Transient expression of bGH in mouse L-cells or endogenous expression of rGH in anterior pituitary cells resulted in an accumulation of GH in the culture medium. Treatment with beta-hydroxyleucine resulted in a block in secretion as evidenced by an accumulation of GHs within these cells. Amino-terminal sequencing of the intracellular form of the analog-substituted GHs demonstrated accurate signal peptide cleavage. In contrast, in vitro translations of bGH RNA performed in the presence of beta-hydroxyleucine and microsomal membranes resulted in the inhibition of signal peptide cleavage. The results suggest that beta-hydroxyleucine can uncouple signal peptide processing and protein secretion in cultured cells.     

Biosynthesis of a ubiouitin-related peptide in rat brain and in human and mouse pituitary tumors

A biosynthetic labeled peptide structurally related to the thymic peptide ubiquitin was first identified fortuitously in bovine pars intermedia cells in regard to its partial NH₂ terminal amino acid sequence (Met 1, Leu 8, 15 and Lys 6, 11, 27, 29, 33) after a protein segment data bank search. A peptide with the same behavior on carboxymethylcellulose chromatography and polyacrylamide gel electrophoresis has been purified after labeling experiments in two areas of rat brain, hypothalamus and striatum, and in a mouse and a human ACTH-secreting pituitary tumors. It represents about 1 to 10% of the total labeled proteins in the various experiments. Its identity with the above mentioned bovine pituitary peptide was confirmed by microsequence analysis with respect to Met 1, Lys 6, 11 in hypothalmus, Met 1 in striatum, and Lys 6, 11, 27, 29, 33 in the two pituitary tumors. The availability of standard purified ubiquitin allowed us to show that labeled and cold peptides have the same electrophoretic mobility and elution volume on Sephadex G-50 chromatography this further confirms their identity. Possible interests of such a biosynthetic characterization of a ubiquitin-related peptide are discussed, particularly in view of the structural relationship of ubiquitin to the non histone component of nuclear protein A-24, and as a test of tissue viability and biosynthetic efficiency in our in vitro biosynthetic systems.     

Somatostatin as a physiological regulator of pulsatile growth hormone secretion

Somatostatin plays an important role in the regulation of the episodic and ultradian rhythm of growth hormone (GH) secretion. Passive immunization of rats with specific antibodies to the 14 and 28 amino acid sequences caused a significant GH elevation. The fact that somatostatin antiserum was unable to block episodic GH surges indicates that this hormone's release must be regulated by a dual mechanism. Indeed, GH-releasing factor (GRF) seems to be instrumental in the maintenance of pulsatile GH secretion. Moreover, exogenous GRF induced a further GH increase predominantly during the period of active secretion. Neutralization of endogenous somatostatin eliminated this time-dependent effect, indicating that this peptide blocks periodical spontaneous GH release. Food deprivation and changes in glucose homeostasis virtually obliterate the ultradian GH rhythm. In this context, peripheral somatostatin seems to play an important role. Also the central GRF/somatostatin interplay is responsible for a short-loop feedback control on pituitary somatotrops.     

De novo sequence analysis of N-terminal sulfonated peptides after in-gel guanidination

Here we report a novel approach in which gel-separated proteins are guanidinated in-gel prior to enzymatic cleavage. In contrast to previously described techniques, this procedure allows the extracted tryptic peptides to be N-terminal sulfonated without any further sample purification. The derivatized peptides were subsequently fragmented using a matrix-assisted laser desorption/ionization time of flight/time of flight instrument. The approach facilitates the de novo sequence analysis and allows obtaining longer stretches of amino acid sequence information. We demonstrate that the obtained information can be used to identify proteins using a sequence similarity search algorithm. The technique was compared to the standard peptide mass fingerprint approach, applied either in-gel or in solution, using a number of sodium dodecyl sulfate-polyacrylamide gel electrophoresis separated model proteins. Finally, the new protocol was applied on a proteomic study of two-dimensional PAGE separated proteins from Shewanella oneidensis. More than 50 proteins from this organism were identified using sub-picomol quantities of protein, and peptide sequences of up to 20 amino acid residues in length have been determined.     

Limited proteolysis study of the structure of chloroplast coupling factor CF1

The structure of chloroplast coupling factor CF1 was studied by limited proteolysis followed by sodium dodecylsulfate polyacrylamide gel electrophoresis and N-terminal sequence analysis. The N-terminal fragment of the alpha-subunit was shown to have an exposed area including the peptide bonds E17--G18, R21--E22, E22--V23, and K24--V25. The cleavage of peptide bonds at amino acid residues E22 or/and V25 caused weaker subunit interactions and partial dissociation of the alpha- and gamma-subunits. In the N-terminal fragment of the isolated CF1 beta-subunit, the L14--E15 bond was found to be exposed to proteolytic attack. Also, the alphaS86--S87, alphaE125--S126, alphaR127--L128, and betaV76--A77 bonds were subject to proteolysis. The correlation between the accessibility of these bonds to proteases and the surface location of similar bonds in mitochondrial F1 was deduced from its molecular structure and a computed model of CF1. The K204--C205 bond exposed to protease on reduction of the CF1 gamma-subunit was shown to be masked when the catalytic reaction was initiated by CaATP.     

Antigenic structure of rabies virus glycoprotein: ordering and immunological characterization of the large CNBr cleavage fragments.

After rabies virus glycoprotein was treated with CNBr, the peptide mixture was fractionated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. CNBr-cleaved peptide fragments were resolved into seven peptide bands under reducing conditions and six peptide bands under nonreducing conditions. The isolated nonreduced polypeptides were further analyzed by electrophoresis under reducing conditions. The N-terminal amino acid sequences were determined for the peptides in each of the isolated bands. The sequence data identified eight CNBr peptides and allowed the peptide fragments to be ordered within the deduced amino acid sequence of the glycoprotein. Analysis of the nonreduced CNBr peptides revealed two conformations of the glycoprotein. Two CNBr peptide fragments were specifically immunoprecipitated with a hyperimmune anti-rabies glycoprotein serum. These two and one other CNBr peptide induced the production of rabies virus-neutralizing antibodies, indicating the existence of at least three distinct antigenic sites on the rabies virus glycoprotein.