The role of arginine residues in interleukin 1 receptor binding

Interleukin 1 (IL-1) is a family of polypeptide cytokines that plays an essential role in modulating immune and inflammatory responses. IL-1 activity is mediated by either of two distinct proteins, IL-1 alpha or IL-1 beta, both of which bind to the same receptor found on T-lymphocytes, fibroblasts and endothelial cells (Type 1 receptor). The effect of specific chemical modification of recombinant IL-1 alpha and IL-1 beta on receptor binding was examined. Modification of the proteins with phenylglyoxal, an arginine-specific reagent, resulted in the loss of Type 1 IL-1 receptor binding activity. The stoichiometry of this modification revealed that a single arginine in either IL-1 alpha or IL-1 beta is responsible for the loss of activity. Cyanogen bromide cleavage of phenylglyoxal modified IL-1 alpha and IL-1 beta, followed by sequencing of the peptides, revealed that arginine-12 in IL-1 alpha and arginine-4 in IL-1 beta, which occupy the same topology in the respective crystallographic structures, are the target of phenylglyoxal. These results suggest that an arginine residue plays an important role in ligand-receptor interaction.

Isolation and partial sequence of goat spleen prothymosin alpha

Goat prothymosin alpha, a highly acidic polypeptide of pI3.5, 109 amino acid residues, has been isolated from lymphoid and non-lymphoid tissues of young female goats. Unlike rat, murine and porcine prothymosins alpha, goat prothymosin alpha appears at a higher concentration in the spleen compared with the thymus. The sequence of segments of the polypeptide involving known mutations has been determined, by automatic sequencing of its tryptic peptide fragments. The acidic amino acid-rich segment in the middle of the molecule, including residues 49-83, has not been sequenced. Goat prothymosin alpha closely resembles bovine prothymosin alpha, with only one substitution, proline for alanine at position 85. It also resembles human prothymosin alpha, with only three substitutions. It differs more significantly from rat and murine prothymosins alpha, by two deletions and three substitutions. The results show the highly conserved nature of the molecule, with substitutions at given positions only.

Purification and amino-terminal sequence of the bovine cardiac sodium-calcium exchanger: evidence for the presence of a signal sequence

The Na(+)-Ca2+ exchange carrier was purified from bovine cardiac tissue by a new procedure which relies principally upon anion-exchange chromatography. The purified protein exhibited two major bands on sodium dodecyl sulfate gels, at 120 and 160 kDa. The relative intensities of the two bands could be altered by variations in the procedures used for preparing the samples for electrophoresis, suggesting that they represent two different conformational states of the same protein. The NH2-terminal amino acid sequences of the 120- and 160-kDa bands were identical and agreed closely with a region of the deduced amino acid sequence of the recently cloned canine cardiac exchanger. The NH2-terminal sequence was preceded in the deduced sequence by a 32-residue segment that exhibited the characteristics of a signal sequence; the initial amino acid in the NH2-terminal sequence followed immediately after the predicted cleavage site for the signal sequence. The Na(+)-Ca2+ exchanger appears to be unique among membrane transport carriers in encoding a cleaved signal sequence. The characteristics of the sequences flanking the first putative transmembrane segment of the mature exchanger suggest that the signal sequence is necessary to ensure the correct topological orientation of the exchanger in the membrane.

Structural analyses of proteins electroblotted from native polyacrylamide gels onto polyvinyldiene difluoride membranes. A method for determining the stoichiometry of protein-protein interaction in solution

The usefulness of a native gel electroblotting technique in the study of protein-protein interactions was demonstrated by the determination of the stoichiometry of the interaction between interleukin-2 (IL-2) and the alpha subunit of IL-2 receptor (IL-2R alpha) in solution. Complexes formed between the recombinant forms of the two proteins in solution were separated from the noncomplexed protein molecules by electrophoresis in a native polyacrylamide gel and the protein bands were electroblotted quantitatively onto polyvinyldiene difluoride membranes for further structural analysis. The data obtained from sequence and amino acid analyses of the blotted proteins provided direct evidence that IL-2 binds to IL-2R alpha in a 1:1 ratio. This methodology should be applicable to the study of other structure/function aspects of protein-protein interactions in solution.

Selective cleavage of polypeptides with trifluoroacetic acid: applications for microsequencing

Cleavage of small polypeptides (less than 30 amino acid residues) by trifluoroacetic acid (TFA) under a variety of reaction conditions including time, temperature, TFA phase, and sample supports has been examined by N-terminal sequencing. Treatment with gas-phase TFA at room temperature will cleave polypeptide chains preferentially at the N-terminal side of serine and threonine residues. When liquid-phase TFA is used, additional cleavage at the C-terminal side of aspartic acid was detected. These procedures are applicable for directly treating samples immobilized on sequencer supports (glass fiber filters or polyvinylidene difluoride membranes) to verify the presence of a polypeptide with a blocked N-terminus as well as to obtain internal sequence data at subnanomole levels.

[Behavior of intermediate filaments in human epithelial cells during mitosis]

By indirect immunofluorescence microscopy and electron microscopy, we studied the behavior of intermediate filaments during mitosis in three human epithelial cell lines, derived from normal epidermis (PcaSE-1, from a cancer patient), stratified epithelium (CNE, from nasopharyngeal carcinoma) and simple epithelium (SPC-A-1 from lung adenocarcinoma) respectively. CNE cells and SPC-A-1 cells express two different intermediate filament systems; keratin filaments and vimentin filaments, but PcaSE-1 cells only express keratin filaments. The keratin filament system in PcaSE-1 cells remained intact and encircled the developing mitotic spindle as the cells entered mitosis. In contrast, in CNE cells and SPC-A-1 cells, keratin filaments appeared to disassemble into amorphous cytoplasmic bodies during mitosis. However, their vimentin filaments remained morphologically intact throughout mitosis. We propose; (1) The disassembly of keratin filaments in mitotic epithelial cells is more or less associated with the degree of their cell malignancy rather than with the abundance of keratin filaments in interphase. (2) Intermediate filaments may be involved in the positioning and/or centering of the spindle during mitosis. (3) The possible function of vimentin filament system in CNE cells is positioning and orientation of chromosomes.

In vitro stability of growth hormone releasing factor (GRF) analogs in porcine plasma

The stability of growth-hormone releasing factor (growth regulating factor; GRF) analogs in porcine plasma was examined. GRF analogs were incubated in porcine plasma at 37 degrees C, extracted and subsequently analyzed using high performance liquid chromatography (HPLC). GRF(1-29)-NH2 was rapidly broken down in the plasma with a degradation rate of t1/2 = 13 min. The primary degradation product was identified as GRF(3-29)-NH2. Substitution of Gly15 by Ala15 slightly prolonged the plasma half-life (t1/2 = 17 min) and the major degradative fragment was found to be [Ala15]GRF(3-29)-NH2. The cleavage between the 2 and 3 position of the peptide was not inhibited by trasylol at a concentration of 1,000 KIU/ml but was dramatically reduced by the combined use of diprotin A and trasylol. Absence of the free amino group at the N-terminus and/or substitution of a D-amino acid residue at the penultimate position completely prevented cleavage between the 2 and 3 position in the structural linear GRF analogs. Side-chain to side-chain cyclization between Asp8 and Lys12 amino acid residues significantly improved the stability of GRF in plasma with t1/2 greater than 2 hr. An additional stability was provided by substitution of D-Ala2 for Ala2 in the structural cyclic analog. Cyclization between Lys21 and Asp25 also improved the stability of the GRF peptide in the plasma. Stability was further enhanced by the presence of D-Ala2 or by forming a dicyclic analog through an additional linkage between Asp8 and Lys12.

Vascular permeability factor: a tumor-derived polypeptide that induces endothelial cell and monocyte procoagulant activity, and promotes monocyte migration

Systemic infusion of low concentrations of tumor necrosis factor/cachectin (TNF) into mice that bear TNF-sensitive tumors leads to activation of coagulation, fibrin formation, and occlusive thrombosis exclusively within the tumor vascular bed. To identify mechanisms underlying the localization of this vascular procoagulant response, a tumor-derived polypeptide has been purified to homogeneity from supernatants of murine methylcholanthrene A-induced fibrosarcomas that induces endothelial tissue factor synthesis and expression (half-maximal response at approximately 300 pM), and augments the procoagulant response to TNF in a synergistic fashion. This tumor-derived polypeptide was identified as the murine homologue of vascular permeability factor (VPF) based on similar mobility on SDS-PAGE, an homologous NH2-terminal amino acid sequence, and recognition by a monospecific antibody to guinea pig VPF. In addition, VPF was shown to induce monocyte activation, as evidenced by expression of tissue factor. Finally, VPF was shown to induce monocyte chemotaxis across collagen membranes and endothelial cell monolayers. Taken together, these results indicate that VPF can modulate the coagulant properties of endothelium and monocytes, and can promote monocyte migration into the tumor bed. This suggests one mechanism through which tumor-derived mediators can alter properties of the vessel wall.

Purification and partial amino acid sequence analysis of two distinct tumor necrosis factor receptors from HL60 cells

Two distinct tumor necrosis factor (TNF) receptors of 55- and 75-kDa apparent molecular masses previously identified on the cell surface by monoclonal antibodies have been solubilized with Triton X-100 from HL60 cells. A filter-based dot blot assay was developed to monitor specific 125I-TNF alpha binding during fractionation of the cell extract. By a combination of immuno- and ligand affinity chromatography and reverse phase high performance liquid chromatography both receptor proteins were purified to apparent homogeneity. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed two bands at 55 and 51 kDa for the 55-kDa TNF receptor and a major 75-kDa and a minor 65-kDa band for the 75-kDa TNF receptor. All these bands specifically bound TNF alpha and TNF beta in ligand blot experiments. The exclusive specificity of monoclonal antibodies of the utr series for the 75.65-kDa bands and of the htr series for the 55.51-kDa bands was demonstrated with the purified antigens on Western blots. Both TNF receptor types were found to contain N-linked carbohydrates. N-terminal amino acid sequence analysis of the 55- and 51-kDa bands of the 55-kDa TNF receptor revealed identical sequences suggesting a possible truncation at the C-terminal end. Two different N-terminal sequences were determined for the 65-kDa band. One corresponded to the published sequence of ubiquitin; the other was therefore assumed to be a unique sequence of the 75-kDa TNF receptor. Additional internal sequences of this receptor were determined after proteolytic cleavage.

Purification and characterization of glycosyl-phosphatidylinositol-specific phospholipase D

We have developed a simple immunoaffinity chromatography procedure for the purification of a glycosyl-phosphatidylinositol (GPI)-specific phospholipase D (GPI-PLD) from bovine serum. The enzyme was initially purified by a procedure consisting of 9% polyethylene glycol precipitation, Q Sepharose anion-exchange chromatography, S-300 gel filtration, wheat germ lectin-Sepharose, hydroxylapatite agarose, zinc chelate matrix, Mono Q-high performance liquid chromatography (HPLC), and Superose 12 (gel filtration) HPLC. Using this purified material as immunogen, we generated a panel of monoclonal antibodies. A low affinity antibody was selected for the purification of catalytically active GPI-PLD from bovine serum by immunoaffinity chromatography, followed by wheat germ lectin-Sepharose and Mono Q-fast protein liquid chromatography. The latter method provides a simple purification procedure with an overall yield of 26%. The purified enzyme has an apparent molecular weight of about 100,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a pI of about 5.6 by isoelectric focusing gel analysis. On Superose 12 HPLC, the material purified by the latter method elutes as a single peak with an apparent molecular weight of 200,000 as determined by protein standards. The enzyme activity is inhibited by [ethylenebis(oxyethylenenitrilo)]tetraacetic acid or 1,10-phenanthroline. Phosphatidic acid is the only 3H-labeled product when [3H]myristate-labeled variant surface glycoprotein is hydrolyzed by the purified enzyme. Amino terminal sequence analysis of the intact 100-kDa protein reveals no strong homology to that of any other known protein. Twelve tryptic peptides derived from the intact protein have been subjected to amino acid sequence analysis. Two of them share sequence homology with each other and with the metal ion binding domains of members of the integrin family. Based upon these criteria, it appears that the purified enzyme is distinct from other phospholipases with specificity for inositol phospholipids.

Purification to homogeneity and partial characterization of cytotoxic lymphocyte maturation factor from human B-lymphoblastoid cells

A cytokine that can synergize with interleukin 2 to activate cytotoxic lymphocytes was purified to homogeneity. The protein, provisionally called cytotoxic lymphocyte maturation factor (CLMF), was isolated from a human B-lymphoblastoid cell line that was induced to secrete lymphokines by culture with phorbol ester and calcium ionophore. The purification method, utilizing classical and high-performance liquid chromatographic techniques, yielded protein with a specific activity of 8.5 x 10(7) units/mg in a T-cell growth factor assay. Analysis of the purified protein by sodium dodecyl sulfate/polyacrylamide gel electrophoresis demonstrated that CLMF is a 75-kDa heterodimer composed of disulfide-bonded 40-kDa and 35-kDa subunits. Determination of the N-terminal amino acid sequences of the two subunits revealed that both subunits are not related to any previously identified cytokine. Purified CLMF stimulated the proliferation of human phytohemagglutinin-activated lymphoblasts by itself and exerted additive effects when used in combination with suboptimal amounts of interleukin 2. Furthermore, the purified protein was shown to synergize with low concentrations of interleukin 2 in causing the induction of lymphokine-activated killer cells.

Two human TNF receptors have similar extracellular, but distinct intracellular, domain sequences

Tumor necrosis factor (TNF) is a cytokine with a wide range of biological activities in inflammatory and immunologic responses. These activities are mediated by specific cell surface receptors of 55 kDa and 75 kDa apparent molecular masses. A 75-kDa TNF receptor cDNA was isolated using partial amino acid sequence information and the polymerase chain reaction (PCR). When expressed in COS-1 cells, the cDNA transfers specific TNF-binding properties comparable to those of the native receptor. The predicted extracellular region contains four domains with characteristic cysteine residues highly similar to those of the 55-kDa TNF receptor, the nerve growth factor (NGF) receptor, and the CDw40 and OX40 antigens. The consensus sequence of the TNF receptor extracellular domains also has similarity to the cysteine-rich sequence motif LIM. In marked contrast to the extracellular regions, the intracellular domains of the two TNF receptors are entirely unrelated, suggesting different modes of signaling and function.

Molecular cloning and expression of the human 55 kd tumor necrosis factor receptor

Two distinct receptors for tumor necrosis factor (TNF) of 55 and 75 kd are expressed at low levels by various cells. The 55 kd TNF receptor was purified from HL60 cells, and partial amino acid sequences were determined. Short degenerate sense and antisense oligonucleotide primers encoding the N- and C-terminal ends of a peptide of 22 amino acid residues were used to amplify a 66 bp cDNA fragment from HL60 RNA by reverse transcriptase-polymerase chain reaction. The cDNA fragment as a probe identified several overlapping clones in a human placenta cDNA library. The open reading frame of the cDNA predicts a 455 amino acid TNF receptor protein with leader, extracellular, transmembrane, and intracellular domains. When expressed in COS-1 cells or in a baculovirus system, the cDNA conferred TNF binding properties comparable to the native receptor. Surprisingly, the 55 kd TNF receptor shows a high degree of sequence homology to the NGF receptor extracellular domain.

Identification of a human immunodeficiency virus-1 protease cleavage site within the 66,000 Dalton subunit of reverse transcriptase

The human immunodeficiency virus-1 reverse transcriptase is a heterodimer of related 51 and 66 kDa subunits. The smaller subunit arises by viral protease-catalyzed cleavage of the carboxy-terminal domain of the 66 kDa species. Comparison of the amino acid composition analyses of the isolated 51 kDa and 66 kDa subunits indicates that the carboxyl terminus of 51 kDa is Phe440. This site was confirmed in vitro using purified recombinant protease and a peptide spanning the postulated cleavage area. The sequence surrounding this site does not show significant homology to other protease cleavage sites in the viral gag and pol precursors; thus, this new information may contribute to our understanding of the sequence specificity of the viral protease.

The use of proteolysis and direct N-terminal sequence analysis to study human interleukin-2/receptor interaction on solid support

An immobilized interleukin-2 receptor which is capable of binding interleukin-2 and suitable for direct N-terminal sequence analysis was employed to study interleukin-2/receptor interactions. Sensitive tryptic sites on the immobilized receptor and its interleukin-2 complex were identified by sequence analyses and compared. The results have revealed that the N-terminal region of interleukin-2 is not involved in receptor binding and the peptide segment covering residues 36-39 in the receptor is probably near or involved in the interleukin-2 binding site. The rapidity and simplicity make this solid phase sequence approach a good method for analyzing interleukin-2/receptor interaction and may be suitable for studying other protein-ligand interactions.

Putative N-terminal sequence of murine soluble immune response suppressor (SIRS): significant homology with short neurotoxin 1

Soluble immune response suppressor (SIRS) is a low-molecular-weight protein (approximately 10,000 daltons) produced by mitogen- or interferon-activated T lymphocytes that can block development of humoral or cell-mediated immune responses in vivo or in vitro. As previously reported, murine SIRS is heterogeneous, eluting in two broad peaks on high performance reverse phase chromatography as well as displaying several broad isoelectric point forms. A putative N-terminal 21 amino acid sequence has been obtained for one of the less hydrophobic isoforms, SIRS-alpha 7. The sequence of SIRS-alpha 7 is unique in mammals but shows a remarkable homology to the family of short neurotoxins (short neurotoxin 1) found in sea snake, adder, and cobra species. A degenerate oligonucleotide probe based on the protein sequence was synthesized and was shown to hybridize to SIRS messenger RNA as measured by SIRS synthesis in a rabbit reticulocyte lysate system. A synthetic polypeptide based on the 21-residue sequence was also prepared and coupled to thyroglobulin or keyhole limpet hemocyanin. These were used to prepare rabbit antisera that neutralize SIRS bioactivity and precipitate authentic SIRS.

Limited proteolysis of recombinant human soluble interleukin-2 receptor. Identification of an interleukin-2 binding core

Limited proteolysis of a recombinant, soluble form of the Tac protein, a human interleukin-2 receptor (rIL-2R), was performed using trypsin, Staphylococcus aureus V8 protease and proteinase K to study the structural requirements of interleukin-2 receptor (IL-2R) for interleukin-2 (IL-2) binding. Sensitive proteolytic sites were found to be clustered in the regions of the polypeptide encoded by exons 3, 5, and 6, with a few semi-sensitive sites located within the two homologous domains encoded by exons 2 and 4. A number of nicked and truncated rIL-2R species generated by proteolysis were assayed for IL-2 binding using recombinant IL-2 (rIL-2) affinity gel and then structurally characterized. The results demonstrated that only the species that consist of the regions encoded by exons 2 and 4, joined by five disulfide bonds, are capable of binding IL-2 and that the presence of semi-sensitive cleavage sites within the two homologous domains had no apparent effect on IL-2 binding. These results suggest that the pattern of the sensitive cleavage sites in rIL-2R is closely related to the structural requirements for IL-2 binding. Based on the experimental results, a highly symmetrical core structure of IL-2R with a total of 135 amino acid residues was identified. This is the smallest protein moiety so far known to be capable of binding IL-2.

Purification of homogeneity and amino acid sequence analysis of a receptor protein for interleukin 1

The interleukin 1 (IL-1) receptor from mouse EL-4 thymoma cells was purified to homogeneity by a method which utilized ligand affinity chromatography and classical chromatographic techniques. After solubilization of the receptor from intact cells with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, the IL-1 binding activity was purified greater than 23,000-fold. Analysis of the purified protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblot, and ligand blot demonstrated that a single protein of molecular mass of approximately 80 kDa is the IL-1 binding polypeptide. The purified protein bound IL-1 with a dissociation constant of approximately 1.1 X 10(-10) M, which is indistinguishable from the affinity of the cell-bound receptor. The amino acid composition of this protein is strikingly similar to the composition deduced from the sequence of a cDNA coding for an IL-1 receptor from EL-4 cells. Protein sequence analysis of Staphylococcus aureus V-8 protease-derived peptides yields data consistent with the sequence proposed from cloned cDNA. These studies have demonstrated that the high affinity IL-1 receptor on EL-4 cells is the 80-kDa protein.

A human immunoglobulin G receptor exists in both polypeptide-anchored and phosphatidylinositol-glycan-anchored forms

Several cDNA clones encoding the human immunoglobulin G receptor CD16 were isolated from human lung or peripheral blood leukocyte cDNA libraries. Nucleotide sequence comparisons revealed that the cDNAs could be divided into two groups. cDNA clones in one group encode a protein that terminates 4 amino acids after the putative transmembrane domain. Clones in the second group encode a protein with an extra 21 amino acids that could comprise a cytoplasmic domain. Direct peptide sequencing was used to determine the N terminus of the mature CD16 receptor protein and supported the existence of the two forms of the receptor. Treatment of neutrophils with phosphatidylinositol-specific phospholipase C resulted in the release of a large percentage of the CD16 molecules from the cell surface. In contrast, treatment of natural killer cells with phosphatidylinositol-specific phospholipase C did not release any CD16 from the cell surface. These data demonstrate that both polypeptide-anchored and phosphatidylinositol-glycan-anchored forms of the CD16 molecule exist and that they are differentially expressed on neutrophils and natural killer cells.

In vitro assembly of 30S and 70S bacterial ribosomes from 16S RNA containing single base substitutions, insertions, and deletions around the decoding site (C1400)

An in vitro system developed for the site-specific mutagenesis of 16S RNA of Escherichia coli ribosomes [Krzyzosiak et al. (1987) Biochemistry 26, 2353-2364] was used to make 10 single base changes around C1400, a residue known to be at the decoding site. C1400 was replaced by U, A, or G, five single base deletions at and to either side of C1400 were made, and C or U was inserted next to C1400. Another mutant possessed seven additional nucleotides at the 3' end of the 16S RNA such that a stem and loop involving the anti-Shine-Dalgarno sequence could form. Each of the mutant RNAs was reconstituted with a complete mixture of 30S proteins to yield 30S ribosomes. Modified in vitro reconstitution conditions were required to obtain assembly of all of the synthetic ribosomes. Quantitative HPLC analysis of the protein content of each mutant showed that all of the proteins were present. The ability of synthetic 30S to form 70S particles under functional assay conditions was about 75% that of natural 30S and was unchanged by any of the mutations except for the deletion of G1401, which decreased the association activity under the standard conditions to 35-40% of synthetic 30S. That part of the ribosomal P site which interacts with the anticodon loop of tRNA was investigated by near-UV (greater than 300 nm) induced cross-linking of AcVal-tRNA. Cross-linking depended on both 30S subunits and the correct codon. The cross-linking yield of all mutants with a pyrimidine at position 1400 was equal to control isolated 30S, and the first-order rate constants for cross-linking of those mutants tested were like reconstituted natural 30S. The site of cross-linking for mutants with a C or U insertion between C1400 and G1401 was shifted to the inserted residue. Cross-linking to the base 5' to G1401 rather than to the residue 3' to C1399 indicates that G1401 is an important structural determinant of the P site.

The use of fluorescamine as a detection reagent in protein microcharacterization

With recent advances in protein microchemistry, compatible methods for the preparation and quantitation of proteins and peptides are required. Fluorescamine, a reagent which reacts with primary amino groups has been used successfully to detect amino acids, peptides, and proteins in various micromethods. This article discusses these methods which include (1) amino acid analysis of protein and peptide hydrolysates with postcolumn fluorescamine derivatization; (2) purification and characterization of proteins and peptides by reversed-phase HPLC with postcolumn fluorescamine derivatization; (3) purification of peptides by two-dimensional chromatography and electrophoresis on thin-layer cellulose with fluorescamine staining; and (4) electroblotting of protein bands from SDS-PAGE to glass fiber filters and polyvinylidene difluoride (PVDF) membranes with fluorescamine staining. In addition, this article also compares a postcolumn fluorescamine detection system with a UV detection system in the applications of amino acid analysis and reversed-phase HPLC protein/peptide analysis.

Molecular cloning of the chicken myelomonocytic growth factor (cMGF) reveals relationship to interleukin 6 and granulocyte colony stimulating factor

Normal as well as retrovirally transformed avian myeloid precursor cells require the colony stimulating factor cMGF for their survival, proliferation and colony formation in vitro. cMGF has been shown to be a glycoprotein which is active in the picomolar concentration range. Co-expression of kinase type oncogenes in v-myb or v-myc transformed myeloid cells induces cMGF expression and confers factor independence via an autocrine mechanism. Here we describe the molecular cloning of cMGF from a myeloblast cDNA library and show that it is a 201 amino acid residue secretory protein which is modified by signal peptide cleavage and glycosylation during translocation into the lumen of membrane vesicles. A bacterially expressed trpE-cMGF fusion protein induces proliferation of E26 transformed myeloblasts in a cMGF bioassay suggesting that glycosylation is not absolutely necessary for biological activity. Sequence comparison reveals that cMGF is distantly related to G-CSF and IL-6.

Molecular cloning and sequencing of the psaD gene encoding subunit II of photosystem I from the cyanobacterium, Synechocystis sp. PCC 6803

Photosystem I reaction center was isolated from the cyanobacterium, Synechocystis sp. PCC 6803, in a form which contains seven different polypeptide subunits. One of the subunits, with a molecular mass of about 16 kDa, was isolated, and protein sequence information was obtained for the amino terminus and several tryptic peptides. Oligonucleotide probes, corresponding to these sequences, were used to probe a genomic library, and the gene, designated psaD, encoding subunit II was cloned and sequenced. The gene encodes a polypeptide with a mass 15,644 Da, which exhibits a high degree of similarity to subunit II from tomato, as well as amino acid sequences reported from barley photosystem I. In addition to this gene, three large open reading frames were identified. Two remain unidentified, and the third is highly homologous to anthranilate synthase, component 1 from Escherichia coli and Saccharomyces cerevisiae.

Cloning of cDNA encoding a 32-kDa protein. An accessory polypeptide of the H+-ATPase from chromaffin granules

The purified H+-ATPase from chromaffin granules is composed of several polypeptides, one of which has an apparent molecular weight of 39,000. Immunoblots with the antibody against this protein and various membrane preparations showed that similar or even identical polypeptides may be associated with the H+-ATPases from synaptic vesicle, kidney microsomes, and lysosomes. A cDNA library was constructed from bovine adrenal medulla, and the cDNA encoding the polypeptide was isolated and sequenced. Search in DNA and protein data banks revealed no significant homology to known genes. Hydrophobicity plot revealed no obvious transmembrane segments with the exception of one stretch of hydrophobic and neutral amino acid starting at leucine 16. The cDNA was shown to encode the entire polypeptide by the virtue of an amino acid sequence corresponding to the N terminus of the open reading frame and by subunit and site-specific antibodies. The cDNA was cloned into an expression vector, transcribed by T7 polymerase, and translated by reticulocyte lysate. Even though the cDNA encodes a protein with a molecular weight of 31,495, the translation product comigrated on sodium dodecyl sulfate gels with the subunit of the purified H+-ATPase. In line with several other subunits of vacuolar H+-ATPases, no signal sequence was detected in the translated gene. Northern blots revealed the presence of a single mRNA of about 1.6 kb in bovine adrenal medulla. However, liver, lung, and kidney may contain additional mRNA of about 1.7 kb.

cDNA sequence encoding the 16-kDa proteolipid of chromaffin granules implies gene duplication in the evolution of H+-ATPases

Vacuolar H+-ATPases function in generating protonmotive force across the membranes of organelles connected with the vacuolar system of eukaryotic cells. This family of H+-ATPases is distinct from the two other families of H+-ATPases, the plasma membrane-type and the eubacterial-type. One of the subunits of the vacuolar H+-ATPase binds N,N'-dicyclohexylcarbodiimide (DCCD) and has been implicated in the proton-conducting activity of these enzymes. We have cloned and sequenced the gene encoding the DCCD-binding protein (proteolipid) of the H+-ATPase of bovine chromaffin granules. The gene encodes a highly hydrophobic protein of 15,849 Da. Hydropathy plots revealed four transmembrane segments, one of which contains a glutamic residue that is the likely candidate for the DCCD binding site. Sequence homology with the vacuolar proteolipid and with the proteolipids of eubacterial-type H+-ATPases was detected. The proteolipids from Escherichia coli, spinach chloroplasts, and yeast mitochondria matched better to the NH2-terminal part of the vacuolar protein. The proteolipids of bovine mitochondria and Neurospora mitochondria matched better to the COOH-terminal end of the vacuolar proteolipid. These findings suggest that the proteolipids of the vacuolar H+-ATPases were evolved in parallel with the eubacterial proteolipid, from a common ancestral gene that underwent gene duplication.

Structural analysis of recombinant soluble human interleukin-2 receptor. Primary structure, assignment of disulfide bonds and core IL-2 binding structure

A purified soluble and functional form of recombinant human interleukin-2 receptor, engineered and expressed in Chinese hamster ovary cells, was structurally characterized. The primary sequence of this 224 amino acid recombinant protein which lacks most of the carboxy-terminal transmembrane and cytoplasmic portions of the intact protein was established by sequence analyses. The disulfide bonds were assigned by comparative peptide mapping of the reduced and non-reduced peptide digests. As in the case of natural interleukin-2 receptor they occur between cysteines 3-147, 46-104, 131-163, and 28/30-59/61. Based on assignment of the disulfide bonds, a structural model of the interleukin-2 receptor for interleukin-2 binding is proposed.

Aspartic acid-484 of nascent placental alkaline phosphatase condenses with a phosphatidylinositol glycan to become the carboxyl terminus of the mature enzyme

A carboxyl-terminal chymotryptic peptide from mature human placental alkaline phosphatase was purified by HPLC and monitored by a specific RIA. Sequencing and amino acid assay showed that the carboxyl terminus of the peptide was aspartic acid, representing residue 484 of the proenzyme as deduced from the corresponding cDNA. Further analysis of the peptide showed it to be a peptidoglycan containing one residue of ethanolamine, one residue of glucosamine, and two residues of neutral hexose. The inositol glycan is apparently linked to the alpha carboxyl group of the aspartic acid through the ethanolamine. Location of the inositol glycan on Asp-484 of the proenzyme indicates that a 29-residue peptide is cleaved from the nascent protein during the post-translational condensation with the phosphatidylinositol-glycan.

Recent microsurgical advances in China

For more than two decades, microsurgery has been developed, practiced, and refined in China. For the most part, this has taken place independent of a parallel process in the Western World. Only until recent years has there been some communication from China regarding this microsurgical experience. The authors believe that there is much yet to be learned from the wealth of Chinese experience in microsurgery, just as Chinese surgeons have gained valuable information from the West. The authors reviewed the microsurgical literature in China from 1983 to 1986, and present here what we regard to be of particular interest to American microsurgeons, including the areas of digital reconstruction, replantation, flap transfer and transposition, and microsurgical techniques and patient management. Some historical background in the development of Chinese microsurgery is also provided.

The cDNA and protein sequences of human lactate dehydrogenase B

Human lactate dehydrogenase B (LDH-B) cDNA was isolated and sequenced. The LDH-B cDNA insert consists of the protein-coding sequence (999 bp), the 5' (54 bp) and 3' (203 bp) non-coding regions, and the poly(A) tail (50 bp). The predicted sequence of 333 amino acid residues was confirmed by amino acid composition and/or sequence analyses of a total of 185 (56%) residues from tryptic peptides of human LDH-B protein. The nucleotide and amino acid sequences of the human LDH-B coding region show 68% and 75% homologies respectively with those of the human LDH-A. The peptide map and amino acid composition data have been deposited as Supplementary Publication SUP 50139 (7 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies are available on prepayment [see Biochem. J. (1987) 241, 5].

Structural characterization of human interferon gamma. Heterogeneity of the carboxyl terminus

Natural human interferon gamma(IFN-gamma) was purified from the conditioned medium of peripheral blood leukocytes using selective silica gel adsorption and antibody-affinity chromatography. SDS-PAGE and Western blot analysis demonstrated three major species with molecular masses of 25 kDa, 20 kDa and 17 kDa. Structural analysis of this natural IFN-gamma preparation demonstrated a pyroglutamate residue at the amino terminus and a heterogeneous carboxyl terminus. The longest and most predominant polypeptide was 138 amino acids in length, which is five residues shorter than the sequence predicted from the cDNA. The presence of multiple-carboxyl-terminal forms indicated possible proteolytic processing during induction or protein purification. Limited proteolytic digestion of full-length recombinant IFN-gamma with endoproteinase Lys-C and trypsin revealed that the carboxyl-terminal 15 residues could be released under conditions in which the core portion of the polypeptide chain remained intact. Thus, the heterogeneity of natural IFN-gamma may be explained by partial proteolytic degradation of the molecule and differences in the degree of glycosylation as previously reported [Rinderknecht, E., O'Conner, B. H. & Rodriguez, H. (1984) J. Biol. Chem. 259, 6790-6797].

Cholecystokinin octapeptides purified from chinchilla and chicken brains

Cholecystokinin octapeptides (CCK8's) have been purified from methanol extracts of 30 chinchilla and 50 chicken brains containing 9.3 nmol and 8.5 nmol of the peptides respectively. Immunoreactive CCK was concentrated on a DEAE trisacryl column and purification effected by two successive HPLC steps. The peptides were each shown to have a sulfated tyrosine. The sequences of the two peptides are compared with the corresponding CCK8's of pig and guinea pig (GP). Chinchilla & GP: D Y V G W M D F; Chicken & pig: D Y M G W M D F. Since chinchilla insulin resembles other mammalian insulins more than does GP insulin, it is of particular interest that the CCK8's of these two species are identical and raises the question as to whether other brain-gut peptides of the chinchilla, which is a New World mammal as is the GP, would resemble those of the GP or the corresponding peptides of Old World mammals.

Proteolytic processing of avian sarcoma and leukosis viruses pol-endo recombinant proteins reveals another pol gene domain

Three pol gene products have been identified in avian retroviral particles: the full-length 95-kilodalton (kDa) beta chain of reverse transcriptase and two proteolytic cleavage products of beta, a 63-kDa reverse transcriptase alpha chain derived from the amino terminus of beta and a 32-kDa (pp32) endonuclease from its carboxy terminus. By using molecularly cloned retroviral DNA and synthetic oligonucleotides to introduce initiator ATGs and codons corresponding to the authentic N termini, we constructed two bacterial-expression clones; one clone contains the entire pol gene, and the other contains the region encoding the pp32 domain. A 99-kDa protein was synthesized in Escherichia coli by the full-length clone, and a 36-kDa protein was synthesized by the endonuclease domain clone. The recombinant proteins exceeded the size of both the mature viral beta chain and the pp32, respectively, by approximately 4 kDa. These larger sizes, however, are consistent with predictions from the DNA sequence of the pol gene. Processing of the recombinant pol proteins was examined by using p15 protease purified from virus particles and antisera directed against synthetic peptides corresponding to three domains in pol. Proteolytic digestion of the 99-kDa product with p15 produced a 63-kDa protein that comigrated on polyacrylamide gels with the alpha chain of reverse transciptase and a 36-kDa fragment that comigrated with the endonuclease domain product. Further digestion of the 36-kDa protein yielded a 32-kDa protein that comigrated with viral pp32 endonuclease. Thus, we concluded that two p15-sensitive sites exist in pol. Cleavage at the previously identified site produces alpha, and cleavage at the newly discovered site removes approximately 4 kDa from the C terminus of the primary protein product. Since the 36-kDa protein was also detected in protein isolated from virus particles, it seems probable that processing at the C-terminal site is a normal step in the production of mature beta and pp32 endonuclease products.

Guinea pig pancreatic polypeptide: structure and pancreatic content

Guinea pig (GP) pancreatic polypeptide (PP) has been purified from an acid-alcohol extract of 6 GP pancreata by a series of 3 HPLC steps. The sequence for GP PP as compared with that of beef and human is shown: (Sequence: see text). In a single GP pancreas weighing 2.4 g the total PP content was 1.0 nmol and the total glucagon content 61 nmol; in a single dog pancreas weighing 35 g the total PP was 385 nmol and the total glucagon 81 nmol. The relatively low content of PP in GP pancreas is consistent with the fact that the GP lacks a ventral pancreas, the region in which PP is found in highest concentration. The high glucagon content of GP pancreas is consistent with that reported in earlier studies.

Purification and molecular characterization of human transcobalamin II

Transcobalamin II (TCII) has been purified from Cohn fraction III of human plasma by batchwise binding to and then elution from carboxymethyl-Sephadex, affinity chromatography using photo-labile aminopropyl cobalamin coupled to activated Sephacryl S-200, and finally chromatography through carboxymethyl cellulose. The yield was approximately 80%. The addition of protease inhibitors in all steps of the purification procedure and extensive washing of the carboxymethyl-Sephadex prior to eluting the TCII minimized degradation of the protein and the final preparation of holo-TCII contained 1 mol of cobalamin/mol of protein. A single polypeptide of 43,000 daltons was obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The NH2-terminal 19 amino acids have been determined for human TCII. 12 of the amino acids are homologous with rabbit TCII and six are homologous with human R-binder, but there is no homology with human intrinsic factor.

Structural heterogeneity and functional domains of murine immunoglobulin G Fc receptors

Binding of antibodies to effector cells by way of receptors to their constant regions (Fc receptors) is central to the pathway that leads to clearance of antigens by the immune system. The structure and function of this important class of receptors on immune cells is addressed through the molecular characterization of Fc receptors (FcR) specific for the murine immunoglobulin G isotype. Structural diversity is encoded by two genes that by alternative splicing result in expression of molecules with highly conserved extracellular domains and different transmembrane and intracytoplasmic domains. The proteins encoded by these genes are members of the immunoglobulin supergene family, most homologous to the major histocompatibility complex molecule E beta. Functional reconstitution of ligand binding by transfection of individual FcR genes demonstrates that the requirements for ligand binding are encoded in a single gene. These studies demonstrate the molecular basis for the functional heterogeneity of FcR's, accounting for the possible transduction of different signals in response to a single ligand.

Isolation, sequence, and developmental profile of a brain-specific polypeptide, PEP-19

By comparing the HPLC profiles of cerebellar extracts from adult and neonatal rats, a developmentally regulated polypeptide, termed PEP-19, was identified. The concentration of PEP-19 rose from 0.1 nmol/g of cerebellum at birth to 2 nmol/g at 20 days postpartum. The polypeptide could also be detected at lower levels in olfactory bulbs of adult rats but was absent in cerebral cortex, brain stem, and all non-neural tissues examined. HPLC-purified PEP-19 contained 61 amino acids and had a molecular size of 7.6 kDa. The native polypeptide is blocked at its amino terminus but was sequenced following proteolytic and chemical fragmentation. The primary amino acid sequence was determined to be: X (S-E) R Q S A G A T N G K D K T S G D N D G Q K K V Q E E F D I D M D A P E T E R A A V A I Q S Q F R K F Q K K K A G S Q S. PEP-19 has a unique sequence, but shares some homology with several calcium binding proteins including the beta chain of S100 and intestinal calcium binding protein. This polypeptide is the primary translation product of cerebellar poly(A)+ mRNA.

Rapid enzymatic degradation of growth hormone-releasing hormone by plasma in vitro and in vivo to a biologically inactive product cleaved at the NH2 terminus

The effect of plasma on degradation of human growth hormone-releasing hormone (GRH) was examined in vitro and in vivo using high performance liquid chromatography (HPLC), radioimmunoassay (RIA), and bioassay. When GRH(1-44)-NH2 was incubated with human plasma, the t1/2 of total GRH immunoreactivity was 63 min (RIA). However, HPLC revealed a more rapid disappearance (t1/2, 17 min) of GRH(1-44)-NH2 that was associated with the appearance of a less hydrophobic but relatively stable peptide that was fully immunoreactive. Sequence analysis indicated its structure to be GRH(3-44)-NH2. Identity was also confirmed by co-elution of purified and synthetic peptides on HPLC. Biologic activity of GRH(3-44)-NH2 was less than 10(-3) that of GRH(1-44)-NH2. After intravenous injection of GRH(1-44)-NH2 in normal subjects, a plasma immunoreactive peak with HPLC retention comparable to GRH(3-44)-NH2 was detected within 1 min and the t1/2 of GRH(1-44)-NH2 (HPLC) was 6.8 min. The results provide evidence for GRH inactivation by a plasma dipeptidylaminopeptidase that could limit its effect on the pituitary.

Guinea pig 33-amino acid gastrin

Only two 34 amino acid gastrin precursors have previously been purified and sequenced, those of pig and of human. The larger molecular form generally accounts for only about 5% of antral gastrin in most species. This report describes the purification of "big gastrin" from guinea pig (GP) antra. Two hundred grams of antra were defatted with acetone and the acetone cakes were extracted with 0.1M NH4HCO3. The extract was concentrated by adsorption onto and batch elution from QA-52 anion exchange cellulose. Fractionation on a mu Bondapak C18 cartridge resolved 3.6 nmol of the larger peptide from 61 nmol of immunoreactive gastrin in the original extract. Two additional HPLC steps brought the peptide to final purity. GP big gastrin is a 33 amino acid peptide with the following sequence: less than ELGPQVPAHLRTDLSKKQGPWAEEEAAYGWMDF# The GP peptide is different from pig G34 in 6 of the 17 NH2-terminal amino acids as well as in the previously reported deletion of a glutamic acid in the COOH-terminus.

Identification of the probable site of choleragen-catalyzed ADP-ribosylation in a Go alpha-like protein based on cDNA sequence

Go alpha, a 39-kDa guanyl nucleotide-binding protein, is functionally and structurally similar to the alpha subunits of the stimulatory and inhibitory guanyl nucleotide-binding proteins (Gs alpha, Gi alpha) of adenylate cyclase and to the alpha subunit of transducin (T alpha), the guanyl nucleotide-binding protein of the retinal photon reception system. A cDNA clone was isolated from a bovine retinal lambda gt10 library by using oligonucleotide probes complementary to sequences in two putative T alpha clones. Partial sequence analysis revealed a deduced amino acid sequence identical to sequences of four tryptic peptides from bovine brain Go alpha. Gs alpha and T alpha are known to serve as substrates for ADP-ribosylation by choleragen. Other workers have established the sequence of the tetrapeptide in T alpha containing the arginine that is ADP-ribosylated and its location in the amino acid sequence deduced from T alpha cDNA. The Go alpha cDNA described here includes a region encoding an amino acid sequence very similar to that surrounding the ADP-ribosylation site in T alpha, consistent with observations that Go alpha can also be a substrate for choleragen. A corresponding sequence in the recently identified Gs alpha cDNA is less homologous to that in T alpha or Go alpha. The reported differences in conditions that promote choleragen-catalyzed ADP-ribosylation of Gs alpha vs. Go alpha could be related to differences in amino acid sequence in the region of the acceptor arginine.

Sequences of gastrins purified from a single antrum of dog and of goat

Heptadecapeptide gastrins (G17) have been purified and sequenced from a variety of species. However, progastrin (G34) sequences have been determined only for pig and human from purified peptides and for rat from cDNA. Since G34 in most species accounts for only approximately 5% of total antral gastrin, micropurification techniques must be employed to avoid the need for large quantities of antral tissue. Efficient purification methodology yielded 1.5 and 1.3 nmol of G34 from the antrum of a single goat and of a single dog, respectively. The N-terminal pyroglutamyl residues were enzymatically removed and the peptides were sequenced through to the proximity of their COOH-termini. The COOH-terminal sequences of goat and dog G34 were confirmed by sequencing the corresponding deblocked G17 from each animal. The previously published dog G17 sequence was shown to be incorrect. The sequences for dog and goat G34 are: Dog less than ELGLQGPPQLVADLSKKQGPWMEEEEAAYGWMDF# Goat less than ELGLQDPPHMVADLSKKQGPWVEEEEAAYGWMDF# Dog and goat gastrins differ in 3 sites in the 17 amino acid NH2-terminus and only a single site in G17 (the sites of differences are underlined). The ratio for sulfated to non-sulfated antral G17 is 9:1 for the goat and 1:9 for the dog.

Guinea pig glucagon differs from other mammalian glucagons

Mammalian glucagon is thought to be highly conserved. Glucagons from pig, cow, human, rat, and hamster have identical amino acid sequences, whereas the amino acid contents of rabbit and camel glucagons are consistent with this 29-amino acid sequence. It had earlier been reported that guinea pig (GP) glucagon contains 40 amino acids. In the current study, glucagon was purified from two GP pancreata by a series of three HPLC steps after acid-alcohol extraction and acetone precipitation. GP glucagon is a 29-amino acid peptide that differs from other mammalian glucagons by substitution of Gln for Asp in position 21, Leu for Val in position 23, Lys for Gln in position 24, Leu for Met in position 27, and Val for Thr in position 29. In view of the marked changes in the COOH-terminal of GP glucagon, receptor binding studies were performed using both rat and GP liver membranes. Labeled synthetic porcine glucagon has similar binding in the two systems and its binding is inhibited to a similar degree by synthetic porcine glucagon, whereas GP glucagon is 10-fold less potent at inhibiting binding in both systems. This suggests that glucagon receptor binding sites in the GP are evolutionarily more conserved than is GP glucagon.

Cholecystokinin-associated COOH-terminal peptides are fully sulfated in pig brain

A radioimmunoassay was developed to detect the cholecystokinin (CCK)-associated nonapeptide (CAP-9) that forms the COOH terminus of pig preproCCK. This peptide (Ser-Ala-Glu-Glu-Tyr-Glu-Tyr-Thr-Ser) is presumably produced at the time that the tyrosine-sulfated octapeptide CCK8(s) is cleaved from preproCCK. Radioimmunoassay of a dried methanol extract of pig brain revealed no detectable CAP-9 immunoreactivity, whereas acid desulfation of the dried methanol extract prior to radioimmunoassay resulted in easily measurable concentrations of CAP-9 immunoreactivity. Two peptides, CAP-9 and des-Ser9-CAP-9, were purified from a methanol extract of 8 kg of commercially obtained whole pig brains. Amino acid analysis showed that each peptide has both tyrosines sulfated. Thus, the likely sequence of CCK post-translational processing events is sulfation of the three tyrosines in the COOH terminus of preproCCK followed by peptide cleavage and appearance of CCK8(s) and CAP-9(s,s).

Partial sequencing of human adult, human fetal, and bovine intestinal alkaline phosphatases: comparison with the human placental and liver isozymes

Purification, molecular weights, amino acid compositions, and partial sequencing of intestinal alkaline phosphatases (EC 3.1.3.1) from human adult, human fetal, and bovine sources is reported. Additional sequence information is presented for the bovine liver isozyme. Comparisons are made of the partial primary structures of intestinal alkaline phosphatases with those of the isozymes from liver and placenta. Homologies among these isozymes provide structural data to corroborate some concepts of the etiology of these isozymes and refute others.

Human liver alkaline phosphatase, purification and partial sequencing: homology with the placental isozyme

Human liver alkaline phosphatase (AP) has been purified to homogeneity. The enzyme has a molecular weight of 150,000 in its native state and consists of two identical subunits of Mr 75,000. After treatment with endoglycosidase F the molecular weight is reduced to 50,000 indicating a high degree of glycosylation. The amino-terminal sequence up to 22 residues was found to be Leu-Val-Pro-Glu-Lys-Glu-Lys-Asp-Pro-Lys-Tyr-(Ala)-Arg-Asp-Gln-Ala-Gln-?- Thr-Leu-Lys-Tyr. The amino-terminal portions of human and bovine liver AP are identical. The amino termini of the human liver and human placental AP isozymes have appreciable homology. Conformationally the amino termini are very similar.

The primary structure of rat parathymosin

Parathymosin has been isolated from rat thymus and from rat liver. Its primary structure is reported as follows: (Sequence; see text). The blocking group at the NH2 terminus was identified by mass spectrometry as acetyl. Regions homologous to amino acid sequences in prothymosin alpha were found to be located between residues 14-20, 23-25, 33-39, 41-43, and 83-87 of parathymosin.