Two distinct families of human and bovine interferon-alpha genes are coordinately expressed and encode functional polypeptides.

The classical human interferon-alpha (HuIFN-alpha) gene family is estimated to consist of 15 or more nonallelic members which encode proteins sharing greater than 77% amino acid sequence homology. Low-stringency hybridization with a HuIFN-alpha cDNA probe permitted the isolation of two distinct classes of bovine IFN-alpha genes. The first subfamily (class I) is more closely related to the known HuIFN-alpha genes than to the second subfamily (class II) of bovine IFN-alpha genes. Extensive analysis of the human genome has revealed a HuIFN-alpha gene subfamily corresponding to the class II bovine IFN-alpha genes. The class I human and bovine IFN-alpha genes encode mature IFN polypeptides of 165 to 166 amino acids, whereas the class II IFN-alpha genes encode 172 amino acid proteins. Expression in Escherichia coli of members of both gene subfamilies results in polypeptides having potent antiviral activity. In contrast to previous studies which found no evidence of class II IFN-alpha protein or mRNA expression, we demonstrate that the class I and class II IFN-alpha genes are coordinately induced in response to viral infection.     

Phosphorylation of beta-crystallin B2 (beta Bp) in the bovine lens

Three major 32P-labeled polypeptides were found in the soluble fraction of bovine lenses cultured in a medium containing [32P]orthophosphate. Two of the polypeptides corresponded to the phosphorylated A and B chains of alpha-crystallin. In this communication, the third polypeptide is now identified. This polypeptide is characterized by a molecular weight of 27,000 and a pI of 6.6, eluted exclusively in the beta Low fraction of a CL-6B gel filtration separation of lens soluble material, and could be further purified by DE52 anion exchange chromatography. The only 32P-labeled amino acid detected was phosphoserine. A single 32P-labeled peptide was observed after tryptic digestion and two-dimensional mapping. The amino acid sequence of the purified peptide is Gly-Ala-Phe-His-Pro-Ser-Ser. This sequence exactly matches the expected C-terminal tryptic fragment, residues 198-204, of the bovine beta-crystallin B2. The results of carboxypeptidase A digestion of the 32P-labeled peptide suggest that only Ser203 is phosphorylated. By using the catalytic subunit of the cAMP-dependent protein kinase, purified beta B2 was phosphorylated in vitro, generating a single 32P-labeled polypeptide with the identical pI as the phosphorylated polypeptide obtained from lens culture. On the basis of these data, the Mr 27,000 32P-labeled polypeptide is identified as the phosphorylated form of the beta-crystallin B2.     

Amino acid and cDNA sequence of bovine phosducin, a soluble phosphoprotein from photoreceptor cells

Vertebrate photoreceptor cells contain a soluble phosphoprotein, phosducin, which complexes with the beta, gamma subunits of the GTP-binding protein, transducin. Light-induced changes in cyclic nucleotide levels modulate the phosphorylation of phosducin by protein kinase A. The complete amino acid sequence of purified phosducin from bovine retinas was determined by Edman degradation from overlapping polypeptides derived from enzymatic digestion by trypsin and Staphylococcus aureus V8 protease or from chemical degradation by cyanogen bromide. Excluding the unidentified group which blocks the NH2 terminus, phosducin contains 245 amino acids with a calculated molecular weight of 28,185 and isoelectric point of pH 4.5. Phosducin is enriched with acidic and sulfur-containing amino acids, having 32 glutamic acid, 16 aspartic acid, 9 methionine, and 5 cysteine residues. It also contains 24 serine and 8 threonine residues, of which only serine 73 is located within a consensus phosphorylation sequence (-RKMS(P)QV-) for cyclic nucleotide-dependent protein kinase. Secondary structure analysis predicts the presence of 62% alpha-helix, 22% beta-sheet, and 16% random coil, with eight turns. Computer-aided searches of protein data banks revealed no apparent homology to any sequenced protein except that coded by a MEKA cDNA clone (Kuo, C-H., Akiyama, M., and Miki, N. (1989) Mol. Brain Res. 6, 1-10) which deviates from the confirmed phosducin sequence in the last 15 amino acids. Sequence analysis of a cDNA clone for bovine retinal phosducin confirmed that the MEKA clone deviation resulted from an unidentified cDNA guanosine nucleotide, a shifted reading frame and a premature stop codon.     

Leucine aminopeptidase from Arabidopsis thaliana. Molecular evidence for a phylogenetically conserved enzyme of protein turnover in higher plants.

Leucine aminopeptidases are exopeptidases which are presumably involved in the processing and regular turnover of intracellular proteins; however, their precise function in cellular metabolism remains to be established. Towards this goal, a full-length complementary DNA encoding a plant leucine aminopeptidase was isolated from a cDNA library of Arabidopsis thaliana and sequenced. The nucleotide sequence showed 49.5% identity to the Escherichia coli xerB-encoded leucine aminopeptidase. Sequence analysis revealed that the cDNA encodes a polypeptide of 520 amino acids with a calculated molecular mass of 54,506 Da. The C-terminal part (amino acids 200-520) of the deduced amino acid sequence showed 43.8% sequence identity to the xerB-encoded leucine aminopeptidase and 42.6% sequence identity to the amino acid sequence of bovine lens leucine aminopeptidase (EC 3.4.11.1). No sequence similarity (not even over short sequence elements) was observed with any other known peptidase or proteinase sequence. The cDNA was expressed as a fusion protein from the lacZ promoter in E. coli. Enzymatic analysis proved that the cloned cDNA encoded an active leucine aminopeptidase. The properties of this enzyme, including metal requirements, inhibitor sensitivity, pH optimum and the remarkable temperature stability, are very similar to those reported for leucine aminopeptidases from other tissues. Amino acids involved in metal and substrate binding in bovine lens aminopeptidase are completely conserved in the plant enzyme as well as in the XerB protein. Our results show that leucine aminopeptidases form a superfamily of highly conserved enzymes, spanning the evolutionary period from the bacteria to animals and higher plants. This is the first aminopeptidase cloned from a plant.     

Ubiquitin is a component of polypeptides purified from corpora amylacea of aged human brain

Corpora amylacea (CA) are one of the conspicuous features of brain tissue in normal aging and neurodegenerative diseases. Quantitative protein determination of purified CA revealed a protein content of about 4% of total weight. Qualitative protein analysis revealed a broad range of polypeptides, with four being more abundant. High performance liquid chromatography (HPLC), fractionation of this protein material showed four peaks which are related to the four major polypeptides with molecular weights of 24 KD, 42 KD, 94 KD, and 133 KD. Amino acid content analysis of the 24 KD, 42 KD and 94 KD polypeptides indicated that distinct protein species are involved. N-terminal amino acid sequence analysis of the 24 KD and 42 KD polypeptides revealed in both cases homology with the N-terminal sequence of human ubiquitin.     

Chromogranin from normal human adrenal glands: purification by monoclonal antibody affinity chromatography and partial N-terminal amino acid sequence

A method is presented for the purification of human chromogranin from adrenal glands obtained at autopsy. The procedure involved homogenization of whole glands in aqueous buffer, salt precipitation, affinity chromatography using a highly specific monoclonal antibody (LK2H10) and reverse-phase high-pressure liquid chromatography. Chromogranin purified from autopsy adrenal glands revealed a high degree of polypeptide heterogeneity when analyzed by silver-stained SDS polyacrylamide gels. Greater than 90% of the protein was represented by a cluster of polypeptides with an Mr = 70 000 (i.e. chromogranin A), while the remaining protein was highly disperse in molecular weight. That these various polypeptides were in fact chromogranin was shown by Western blotting using monoclonal antibody LK2H10. About 6 nmol of chromogranin were obtained from 97 g of starting adrenals which was estimated to be a 25% yield and a 250-fold enrichment from adrenal homogenates. Critical to achieving reasonable yields of this protein was the need for particular low pH buffers for resuspension of chromogranin after solvent removal steps. Chromogranin purified from human adrenal glands was similar in amino acid composition, and identical in the N-terminal amino acid sequence (24 residues) to bovine chromogranin A. A secondary sequence representing 25% of the total protein and missing the first three residues of the N-terminus suggested the possibility of N-terminal processing of chromogranin in situ. The conservation of the N-terminal amino acid sequence of human and bovine chromogranin contrasts with the strong sequence variability predicted by antisera cross-reactivity and suggests that the N-terminus of chromogranin may be critical for its biological activity.     

The amino acid sequence of the 9 kDa polypeptide and partial amino acid sequence of the 20 kDa polypeptide of mitochondrial NADH:ubiquinone oxidoreductase.

Mitochondrial NADH:ubiquinone oxidoreductase (complex I) is the most complicated enzyme in the respiratory chain and is composed of at least 26 distinct polypeptides. Two hydrophilic subfractions of bovine heart complex I were systematically resolved into individual polypeptides by chromatography. Three polypeptides (51, 24, and 9 kDa) were isolated from the flavoprotein fraction (FP) of complex I, and the complete amino acid sequence of the 9 kDa polypeptide was determined. The 9 kDa polypeptide is composed of 75 amino acids with a molecular weight of 8,437. This protein exhibits no obvious sequence similarity to other proteins. The iron-sulfur protein fraction (IP) of complex I was separated into eight polypeptides, 75, 49, 30, 20, 18, 15, 13 kDa-A, and 13 kDa-B. The 20 kDa polypeptide was recognized as a novel component of IP for the first time. The N-terminal and several peptide sequences of the 20 kDa polypeptide were determined. Comparison of the sequences revealed significant sequence similarities of the 20 kDa polypeptide to the psbG gene products encoded in the chloroplast genome. The conserved sequence in these proteins was also found in the small subunit of the nickel-containing hydrogenases. These results suggest that complex I is related to other redox enzyme complexes.     

The amino acid sequences of two 13 kDa polypeptides and partial amino acid sequence of 30 kDa polypeptide of complex I from bovine heart mitochondria: possible location of iron-sulfur clusters

Mitochondrial NADH:ubiquinone oxidoreductase (complex I) is the most complicated system in the respiratory chain. It consists of many subunits, some of which hold iron-sulfur clusters, but structural information is still limited. The amino acid sequences of two 13 kDa polypeptides, 13 kDa-A and 13 kDa-B polypeptides, of iron-sulfur protein fraction (IP) of bovine heart mitochondrial complex I were determined by a combination of protease digestion, Edman degradation, and carboxypeptidase digestion. The 13 kDa-A polypeptide was composed of 96 amino acids with a molecular weight of 10,536. The 13 kDa-B polypeptide consisted of 114 amino acids and had an acetylated amino terminus. The molecular weight of this protein was calculated to be 13,130 including the acetyl group. These proteins had no obvious sequence similarity to other known proteins. The partial amino acid sequence of 30 kDa-B polypeptide of IP was also determined to reveal a characteristic arrangement of cysteine residues that could be involved in iron-sulfur cluster formation.     

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.     

Cloning and sequence determination of human placental aldose reductase gene

The human aldose reductase gene has been cloned by screening a human placental cDNA library with antibodies against bovine lens aldose reductase. The nucleotide sequence of the entire coding region has been determined. The deduced amino acid sequence indicates that the human enzyme is 84% identical to the bovine lens aldose reductase and 85% identical to the rat lens aldose reductase. It is also very similar to the human aldehyde reductase, the bovine prostaglandin F synthase, and to the European common frog rho-crystallin. The deduced amino acid sequence also indicates that maturation of aldose reductase involves removal of the N-terminal methionine.     

Accumulation of cell-bound alpha-amylase in Bacillus subtilis cells in the presence of tunicamycin

The amino acid sequence of the N-terminal cyanogen bromide fragment of bovine lens leucine aminopeptidase has been determined. This fragment contains a total of 171 amino acid residues and has a calculated molecular weight of 18,637. The sequence data presented here represent the first report of primary structure determination of a member of the class of aminopeptidases.The single cleavage site produced by limited tryptic digestion of native leucine aminopeptidase was determined to be between arginine-137 and lysine-138 of the total amino acid sequence. The possible existence of distinct structural domains in leucine aminopeptidase is discussed.     

Monoclonal antibodies to a proenkephalin A fusion peptide synthesized in Escherichia coli recognize novel proenkephalin A precursor forms

Monoclonal antibodies have been generated to a chimeric peptide comprised of Escherichia coli beta-galactosidase fused to the amino acid sequence 69-207 of human preproenkephalin A. Two monoclonal antibodies, PE-1 and PE-2, were identified by their ability to recognize the same segment of proenkephalin A fused to the cII gene product of the E. coli bacteriophage lambda. The binding domains of PE-1 and PE-2 have been broadly located, with respect to the primary translation product, within the amino acid sequences 152-207 and 84-131, respectively. Immunoblot analysis of total bovine adrenomedullary chromaffin granule lysate reveals PE-1 and PE-2 immunoreactive forms of observed molecular mass 35, 33, 29, 24, 22, and 15 kDa, and an 18-kDa PE-1 immunoreactive form. Separation of granule membranes from their contents reveals differential membrane association of these high molecular weight polypeptides. There is preliminary evidence that PE-1 may be detecting a subset of polypeptides where shortening from the NH2 terminus has occurred. We postulate that the 35-kDa form represents the intact bovine enkephalin precursor of predicted molecular mass 27.3 kDa. This experimental approach should be generally applicable to the generation of antibodies which will recognize intact peptide precursors together with their post-translational cleavage products.     

The primary structure of human Rieske iron-sulfur protein of mitochondrial cytochrome bc1 complex deduced from cDNA analysis

We isolated a cDNA encoding human Rieske Fe-S protein of mitochondrial cytochrome bc1 complex from a fibroblast cDNA library by colony hybridization. The cDNA contains the nucleotide sequence encoding all of the amino acids (274 residues) comprising the putative precursor to the protein. Based on the known amino acid sequence of bovine Rieske Fe-S protein, the N-terminal extension sequence is presumed to be composed of 78 amino acids with a molecular weight of 8053. The mature protein consists of the same number of amino acid residues as that of its rat and bovine counterparts, having a homology of about 92% with the latter.     

Functional Elements in Molecular Chaperone α-Crystallin: Identification of Binding Sites in αB-Crystallin

α-Crystallin, the predominant eye lens protein with sequence homology to small heat shock proteins, acts like a molecular chaperone by suppressing the aggregation of damaged crystallins and proteins. To gain an insight into the amino acid sequences in α-crystallin involved in chaperone-like function, we used a cleavable, fluorescent, photoactive, crosslinking agent, sulfosuccinimidyl-2(7-azido-4-methylcoumarin-3-acetamido)-ethyl-1,3′ dithiopropionate (SAED), to derivatize yeast alcohol dehydrogenase (ADH) and allowed it to complex with bovine α-crystallin at 48°C. The complex was photolyzed and reduced with DTT and the subunits of α-crystallin, αA- and αB-, were separated. Fluorescence analysis showed that both αA- and αB-crystallins interacted with ADH during chaperone-like function. Tryptic digestion, amino acid sequencing, and mass spectral analysis of αB-crystallin revealed that APSWIDTGLSEMR (57-69) and VLGDVIEVHGKHEER (93-107) sequences were involved in binding with ADH.     

Bovine pancreatic trypsin inhibitor and homologous polypeptide inhibitors in nephron cells.

Bovine pancreatic trypsin inhibitor (BPTI, aprotinin) is a fifty-eight amino acid polypeptide, which is present together with related molecular isoforms in various bovine organs. In the present study these protease inhibitors were isolated from bovine kidney by affinity chromatography on immobilized trypsin and a subsequent FPLC step. Due to their electrophoretic, structural, and inhibitory properties, the inhibitors were strictly similar to the polypeptides identified previously in other bovine organs. Immunohistochemical experiments showed a widespread localization of these polypeptides in nephron epithelial cells (proximal and distal tubules, loop of Henle, collecting tubules).     

Distribution,Molecular Structure and Functional Analysis of Carnitine Transporter (SLC22A5) in Canine Lens Epithelial Cells

While carnitine has been reported to have an anti-oxidative role on the ocular surface, there has been no report on the existence of a carnitine transporter (SLC22A5) in the lens. Therefore, we investigated the carnitine transport activity of canine lens epithelial cells (LEC) and determined the molecular structure of canine SLC22A5. The carnitine transport activity was 7.16 ± 0.48 pmol/mg protein/30 min. Butyrobetaine, the analogue of carnitine, reduced 30% of the activity at 50 µM. A coding sequence of canine carnitine transporter was 1694 bp long and was predicted to encode 557 amino acid polypeptides. The deduced amino acid sequence of canine carnitine transporter showed >80% similarity to that of mouse and human. Western blot analysis detected the band at 60 kDa in the membrane of lens epithelial cells. The high content of carnitine in the lens is possibly transported from aqueous humor by SLC22A5.     

Structural similarities between the major polypeptides of thylakoid membranes from Chlamydomonas reinhardtii

The major polypeptides of thylakoid membranes from Chlamydomonas reinhardtii were purified by preparative gel electrophoresis and examined for structural similarities. The largest of these polypeptides has an apparent molecular mass of 29,500 ± 500 daltons, whereas the other two both have an apparent mass of 26,000 ± 500 daltons. The amino acid compositions and uv-absorption spectra of the 29K- and 26K-dalton polypeptides are very similar. The same pattern of release of amino acids was obtained from both fractions by digestion with carboxypeptidase Y. Endoproteolytic digestion with trypsin, chymotrypsin, staphylococcal protease, and mild acid yielded identical patterns of N-terminal amino acids from both the 29K- and 26K-dalton polypeptides. However, different patterns of peptides were found after electrophoresis of fragments generated by digestion with staphylococcal protease. Conditions of electrophoresis were defined that permitted separation of the 26K-dalton fraction into two components, designated as polypeptides 16 and 17 in the identification system of Chua and Bennoun (1975, Proc. Nat. Acad. Sci. USA72, 2175–2179). Amino acid compositions of these two polypeptides are nearly identical. Polypeptide 16 contained N-terminal isoleucine, but no free N-terminal amino group was detected in polypeptide 17. Electrophoretic analysis of staphylococcal protease digests of these two polypeptides revealed significant differences in the patterns of peptides. These data confirm that there are three distinct major polypeptides in these membranes, which are present at nearly equal amounts. However, the data also suggest that significant similarities in amino acid sequence exist between these polypeptides.     

Complete amino acid sequences of bovine and human endozepines. Homology with rat diazepam binding inhibitor

The complete amino acid sequences of bovine and human brain endozepines have been determined. The amino-terminal serine of both endozepines is acylated. Assignment of the first 7 residues was achieved through Edman degradation after acid-induced rearrangement and subsequent acid hydrolysis of the amino-terminal blocking group. Cleavage of endozepine by chemical and enzymatic techniques established all the fragments in an unambiguous sequence. Bovine and human endozepines are single-chain polypeptides of 86 residues, with calculated molecular weights of 9913, displaying 93% homology. A comparison between the sequences of bovine and human endozepines with the partial sequences of the functionally related diazepam binding inhibitor from rat brain reveals significant sequence homology. The reported results suggest that bovine and human endozepines as well as rat diazepam binding inhibitor belong to a new family of polypeptides which presumably take part in the modulation of gamma-aminobutyric acid-ergic transmission.     

Characterization of the Rickettsia prowazekii pepA gene encoding leucine aminopeptidase.

The pepA gene, encoding a protein with leucine aminopeptidase activity, was isolated from Rickettsia prowazekii, an obligate intracellular parasitic bacterium. Nucleotide sequence analysis revealed an open reading frame of 1,502 bp that would encode a protein of 499 amino acids with a calculated molecular weight of 53,892, a size comparable to that of the protein produced in Escherichia coli minicells containing the rickettsial gene. Also, heat-stable leucine aminopeptidase activity was demonstrable in an E. coli peptidase-deficient strain containing R. prowazekii pepA. Comparison of the amino acid sequence of the R. prowazekii PepA with the characterized leucine aminopeptidases from E. coli, Arabidopsis thaliana, and bovine eye lens revealed that 39.8, 34.9, and 34.0% of the residues were identical, respectively. Residues proposed to be part of the active site or involved in the binding of metal ions in the bovine metalloenzyme were all conserved in R. prowazekii PepA. However, despite the structural and enzymatic similarity to E. coli PepA, the R. prowazekii protein was unable to complement the cer site-specific, PepA-dependent recombination system found in E. coli that resolves ColE1-type plasmid multimers into their monomeric forms.