Cloning and characterization of an odorant receptor in five Pacific salmon

The olfactory system of fish is extremely important as it is able to recognize and distinguish a vast of odorous molecules involved in wide ranges of behaviors including reproduction, homing, kin recognition, feeding and predator avoidance; all of which are paramount for their survival. We cloned and characterized one type olfactory receptors (ORs) from five congeneric salmonids: lacustrine sockeye salmon (Oncorhynchus nerka), pink salmon (O. gorbuscha), chum salmon (O. keta), masu salmon (O. masou) and rainbow trout (O. mykiss). Lacustrine sockeye salmon olfactory receptor 1 (LSSOR1) showed high sequence homology to the OR subfamily, and was expressed only in the olfactory epithelium (as indicated by PCR amplified genomic DNA and cDNA). OR genes from the five salmonids examined all showed strong homology (96-99%) to each other. Hypervariable regions, believed to be ligand-binding pockets, showed homologous completely matched amino acid sequences except for one amino acid in pink salmon olfactory receptor 1 (PSOR1), revealing that these ORs may be well conserved among salmon species. These results suggest that the isolated 5 salmonid ORs might play an important role in salmon life cycles.     

Comparative studies of catalase and superoxide dismutase activity within salmon fish erythrocytes

1. Superoxide dismutase isolated from erythrocytes of several species of salmon and the rainbow trout exhibited single electrophoretic bands of activity which migrated anodally similar to the human erythrocyte enzyme; two discrete bands were observed for the coho salmon. 2. No polymorphism was observed for 30 samples from sockeye salmon and six samples from king salmon. Only one sample of rainbow trout (one of 12) exhibited an electrophoretic mobility difference. 3. Catalase migration on starch-gel resembled the human enzyme's electrophoretic mobility for all salmon species and rainbow trout. Catalase activity of the sockeye salmon (2929 +/- 895 mumol min-1 gHb-1) was determined to be lower than human catalase activity. 4. All samples differed from the human enzymes in that they required the presence of a detergent, Triton X-100, for solubilization.     

Amino acid sequence of alpha-chain of hemoglobin IV from trout (Salmo irideus)

The amino acid sequence of the alpha-chain of trout hemoglobin (Hb) IV is given, thus completing the primary structure of the hemoglobin component of trout's blood characterized by the Root effect. The trout Hb IV alpha-chain consists of 142 amino acid residues; comparison with the corresponding sequences from human and carp hemoglobins shows differences of 50.0 and 35.9%, respectively. A difference of 39.6% is found with the alpha-chain of trout Hb I, the other major hemoglobin component of trout blood, devoid of heterotropic effects.     

Sequence analysis and tissue expression of a non-Bohr beta-globin cDNA from Atlantic salmon

The presence of a haemoglobin protein which does not exhibit a Bohr effect has been found only in fish living in fast flowing waters. We report the cloning of the first non-Bohr effect beta-globin cDNA from an adult Atlantic salmon kidney bank. Nucleotide sequence analysis of this cDNA shows that the predicted beta-globin peptide comprises 147 amino acids with a calculated molecular mass of 15 975 Da and an overall amino acid homology of 40 to 50% to higher vertebrates and 60–90% to fish sequences. This sequence confirms the important amino acid residues which are changed thus causing loss of the Bohr effect [Powers, D.A. and Edmunson, A.B. (1972) Multiple hemoglobins of catostomid fish. J. Biol. Chem. 247, 6686–6693; Brunori, M. (1975) Molecular adaptation to physiological requirements: the hemoglobin system of trout. Curr. Topics Cell. Regul. 9, 1–39]. This loss allows the haemoglobin protein to have a higher oxygen affinity, as it does not release oxygen when the pH of the surrounding environment decreases, which is an important ability for the fish in times of stress.     

High levels of MHC class II allelic diversity in lake trout from Lake Superior

Sequence variation in a 216 bp portion of the major histocompatibility complex (MHC) II B1 domain was examined in 74 individual lake trout (Salvelinus namaycush) from different locations in Lake Superior. Forty-three alleles were obtained which encoded 71-72 amino acids of the mature protein. These sequences were compared with previous data obtained from five Pacific salmon species and Atlantic salmon using the same primers. Although all of the lake trout alleles clustered together in the neighbor-joining analysis of amino acid sequences, one amino acid allelic lineage was shared with Atlantic salmon (Salmo salar), a species in another genus which probably diverged from Salvelinus more than 10-20 million years ago. As shown previously in other salmonids, the level of nonsynonymous nucleotide substitution (dN) exceeded the level of synonymous substitution (dS). The level of nucleotide diversity at the MHC class II B1 locus was considerably higher in lake trout than in the Pacific salmon (genus Oncorhynchus). These results are consistent with the hypothesis that lake trout colonized Lake Superior from more than one refuge following the Wisconsin glaciation. Recent population bottlenecks may have reduced nucleotide diversity in Pacific salmon populations.     

Characterization of a cDNA clone encoding a Brassica napus 12 S protein (cruciferin) subunit. Relationship between precursors and mature chains

Cruciferin (12 S globulin) is a large, neutral, oligometric protein synthesized in rapeseed (Brassica napus) during seed development. It is the major seed protein and is composed of six subunit pairs. Each of these pairs is synthesized as a precursor containing one heavy alpha-chain and one light beta-chain. Electrophoretic analysis of cruciferin showed that four different alpha- and four different beta-chains exist. A cruciferin clone was selected from an embryo cDNA library. This clone, pCRU1, contains a 1518-base pair open reading frame corresponding to a truncated NH2-terminal signal sequence followed by an alpha-chain of 296 and a beta-chain of 190 amino acid residues. Individual cruciferin chains as well as peptides thereof were subjected to NH2-terminal amino acid sequence analysis. The sequences obtained from a specific alpha- and beta-chain pair (alpha 1 and beta 1) showed total identity with the deduced amino acid sequence from pCRU1. Further comparisons revealed that a previously characterized cruciferin cDNA clone encodes one of the precursors for the closely related alpha 2/ alpha 3-beta 2/beta 3 subunits. The deduced amino acid sequences of the two cDNA clones display 64% similarity.     

Development and characterization of a competitive polyclonal antibody enzyme-immunoassay for salmon insulin-like growth factor-II

This paper describes the development and validation of a competitive, polyclonal antibody enzyme-immunoassay (EIA) for the measurement of salmon and trout insulin-like growth factor-II (IGF-II). A polyclonal antiserum was raised against a synthetic peptide epitope, corresponding to amino acid residues 1-9 of the N-terminus of mature Atlantic salmon (Salmo salar) IGF-II. The antiserum was purified by hydrophobic charge induction chromatography (HCIC). The partially purified immunoglobulins were used in an enzyme-immunoassay system (EIA) resulting in a highly specific assay for salmon IGF-II with cross-reactivity of less than 0.01% for recombinant salmon IGF-I and recombinant salmon growth hormone (GH), and 5.57% for salmon insulin (sIns). The recombinant salmon IGF-II (rsIGF-II) standard curve limit of detection was 1.37 ng/ml with an EC(50) of 44.97+/-0.82 ng/ml. Intra- and interassay coefficients of variation were determined at 7.47% (n=15) and 7.42% (n=15), respectively. Added rsIGF-II was adequately recovered from acid-treated Atlantic salmon and rainbow trout (Oncorhynchus mykiss) plasma samples. Parallel dose-response inhibition curves were demonstrated for the plasma of both fish species tested. Circulating IGF-II levels of 22.26+/-2.66 and 18.24+/-1.43 ng/ml were determined for acid-treated plasma of normal adult Atlantic salmon and rainbow trout, respectively. This EIA should prove to be useful in the study of factors which influence circulating plasma levels of IGF-II in these fish species.     

Purification and characterization of cathepsin D from herring muscle (Clupea harengus)

Cathepsin D was purified and concentrated 469-fold from a homogenate of Clupea harengus muscle. The purified enzyme is a monomer with a molecular weight of 38000-39000. It is inhibited by pepstatin and has optimal activity at pH 2.5 with hemoglobin as the substrate. The isoelectric point is at pH 6.8. Glycosidase treatment and binding to Concanavalin A indicated that the enzyme contains one N-linked carbohydrate moiety of the high-mannose type per molecule. The first 21 amino acid residues of the N-terminal showed high similarity to cathepsin D from antarctic icefish liver (Chionodraco hamatus) and trout ovary (Oncorhynchus mykiss). Digestion of the beta-chain of oxidized insulin resulted in preferential cleavage at Leu(15)-Tyr(16), (47%), Tyr(16)-Leu(17) (34%) and Ala(14)-Leu(15) (18%). Incubation with myofibrils from herring muscle at pH 4.23 showed that the enzyme mainly degraded myosin, actin and tropomyosin.     

Structure of the human adult hemoglobin minor fraction A1b by electrospray and secondary ion mass spectrometry. Pyruvic acid as amino-terminal blocking group

Hemoglobin A1b is a minor hemoglobin component from human hemolysate (less than 0.5% of total hemoglobin) whose structure has never been established. It was purified and studied by mass spectrometry. Electrospray ionization of its abnormal beta-chain indicated a 70-Da mass increase. Separation of the trytic digest by reversed-phase liquid chromatography revealed an abnormal beta T1 peptide. Cesium ion bombardment ionization produced a protonated molecular ion at m/z 1022.516, showing an additional C3H2O2 residue to normal beta T1. The amino acid sequences of both abnormal and normal beta T1 peptides were found identical by comparison of their collision activation spectra. Time course hydrolysis of abnormal beta T1 indicated a rapid loss of the modifying group, leading to normal beta T1. At least, mild treatment with acidic methanol showed an additional methylated site, comparatively with normal beta T1. All these results are consistent with a ketimine-linked pyruvic acid at the amino end of the beta-chain of hemoglobin.     

Salmonid olfactory system-specific protein (N24) exhibits glutathione S-transferase class pi-like structure

A salmonid olfactory system-specific protein (N24) that has been identified in lacustrine sockeye salmon (Oncorhynchus nerka) was characterized by biochemical and molecular biological techniques. N24 is a homodimer, and the intact molecular mass is estimated as approximately 43.3 kDa by gel filtration. Furthermore, N24 was located only in the cytosolic fraction of the olfactory tissues as determined by subcellular fractionation. cDNA encoding the lacustrine sockeye salmon N24 was isolated and sequenced. This cDNA contained a coding region encoding 216 amino acid residues and the molecular mass of this protein is calculated to be 242,224.77. The protein and nucleotide sequencing demonstrates the existence of a remarkable homology between N24 and glutathione S-transferase (GST; EC 2.5.1.18) class pi enzymes. Northern analysis showed that N24 mRNA with a length of 950 bases is expressed in lacustrine sockeye salmon olfactory epithelium. Olfactory receptor cells showed strong hybridization signals for N24 mRNA in the olfactory epithelium. N24 demonstrated glutathione binding activity in affinity-purified GST column experiments. The present study describes for the first time cDNA cloning of GST in fish olfactory epithelium.     

Identification and characterization of a variant of the third component of complement (C3) in rainbow trout (Salmo gairdneri) serum

A rainbow trout serum protein that is cross-reactive with the third complement component of rainbow trout (C3-1) was purified to homogeneity and its structural and functional properties compared with those of C3-1. This protein (termed C3-related protein: C3-2) bears a close structural resemblance to C3-1, although C3-2 apparently shows no hemolytic activity. Like C3-1, C3-2 consists of two disulfide-linked polypeptide chains (128,000 alpha and 72,000 beta) and retains the unique thiol ester site in the alpha-chain. C3-2 shares some antigenicity with C3-1, but it also displays distinctive antigenic determinants of its own. Comparison of tryptic peptide maps revealed that about 20% of the peptides was specific to either C3-1 or C3-2, and about 80% of the peptides were common to both proteins. Amino acid compositions of the alpha- and beta-chains of C3-2 were similar to those of C3-1. Furthermore, amino acid sequence analysis of the NH2 termini of the alpha- and beta-chains of C3-2 revealed a high degree of homology with those of C3-1, 24 of 26 residues in the alpha-chain and all 20 in the beta-chain of C3-2 were identical with those found in C3-1. Both C3-1 and C3-2 were detected in all the adult rainbow trout tested and in first generation offspring randomly bred from them.     

Primary structure of myosin heavy chain from fast skeletal muscle of Chum salmon Oncorhynchus keta

The nucleotide sequence of the cDNA encoding myosin heavy chain of chum salmon Oncorhynchus keta fast skeletal muscle was determined. The sequence consists of 5,994 bp, including 5,814 bp of translated region deducing an amino acid sequence of 1,937 residues. The deduced sequence showed 79% homology to that of rabbit fast skeletal myosin and 84-87% homology to those of fast skeletal myosins from walleye pollack, white croaker and carp. The putative binding-sites for ATP, actin and regulatory light-chains in the subfragment-1 region of the salmon myosin showed high homology with the fish myosins (78-100% homology). However, the Loop-1 and Loop-2 showed considerably low homology (31-60%). On the other hand, the deduced sequences of subfragment-2 (533 residues) and light meromyosin (564 residues) showed 88-93% homology to the corresponding regions of the fish myosins. It becomes obvious that several specific residues of the rabbit LMM are substituted to Gly in the salmon LMM as well as the other fish LMMs. This may be involved in the structural instability of the fish myosin tail region.     

Amino acid sequence of the beta-chain of the tetrameric haemoglobin of the bivalve mollusc, Anadara trapezia

The amino acid sequence of the beta-chain of the principal haemoglobin from A. trapezia has been determined. The sequence was deduced from the sequences of tryptic peptides, which were fractionated using highperformance liquid chromatography and peptide mapping. Additional sequence data, particularly for the large tryptic peptides, was obtained from enzyme digests of both cyanogen bromide fragments and large citraconyltryptic peptides. The beta-chain has 151 residues which is longer than all the other sequenced haemoglobin chains except the alpha-chain of A. trapezia, which is 153 residues in length. The residues corresponding to those normally in the D helix are absent in this beta-chain. The additional residues are contributed by an extension of the N-terminal region, which was also found to be acetylated. Comparison of the beta-chain amino acid sequence with that of the alpha-chain of A. trapezia, the dimeric chain of A. trapezia, and the dimeric chain of A. broughtonii showed 53% identity in each case. In the E and F helices, the homology is particularly noticeable. There is 100% homology in the F helix of all four chains. The dimeric globin of A. trapezia also shows 100% homology with the beta-chain in the E helix, while the alpha-chain shows 75%. If the tertiary structure of the alpha- and beta-chains of A. trapezia haemoglobin is the same as that of horse haemoglobin, then there are many changes in the alpha 1 and beta 2 contact site residues.     

Comparison of two aquatic alphaviruses,salmon pancreas disease virus and sleeping disease virus,by using genome sequence analysis,monoclonal reactivity,and cross-infection

Cell culture isolates of salmon pancreas disease virus (SPDV) of farmed Atlantic salmon and sleeping disease virus (SDV) of rainbow trout were compared. Excluding the poly(A) tracts, the genomic nucleotide sequences of SPDV and SDV RNAs include 11,919 and 11,900 nucleotides, respectively. Phylogenetic analysis places SPDV and SDV between the New World viruses of Venezuelan equine encephalitis virus and Eastern equine encephalitis virus and the Old World viruses of Aura virus and Sindbis virus. When compared to each other, SPDV and SDV show 91.1% nucleotide sequence identity over their complete genomes, with 95 and 93.6% amino acid identities over their nonstructural and structural proteins, respectively. Notable differences between the two viruses include a 24-nucleotide insertion in the C terminus of nsP3 protein of SPDV and amino acid sequence variation at the C termini of the capsid and E1 proteins. Experimental infections of Atlantic salmon and rainbow trout with SPDV and SDV confirmed that the disease lesions induced by SPDV and SDV were similar in nature. Although infections with SPDV and SDV produced similar levels of histopathology in rainbow trout, SDV induced significantly less severe lesions in salmon than did SPDV. Virus neutralization tests performed with sera from experimentally infected salmon indicated that SPDV and SDV belonged to the same serotype; however, antigenic variation was detected among SDV and geographically different SPDV isolates by using monoclonal antibodies. Although SPDV and SDV exhibit minor biological differences, we conclude on the basis of the close genetic similarity that SPDV and SDV are closely related isolates of the same virus species for which the name Salmonid alphavirus is proposed.     

Methemoglobin reductase activity in fish erythrocytes

NADH-methemoglobin reductase activity of erythrocytes from the coho salmon, Oncorhynchus kisutch, sockeye salmon, Oncorhynchus nerka, and the rainbow trout, Salmo gairdneri exhibited a major band of activity that resembled the human enzyme in electrophoretic mobility. No polymorphism was found in 35 samples from rainbow trout, 4 samples from Dolly Varden, 29 samples from sockeye salmon, and 24 samples from coho salmon. All samples differed from the human enzyme in that they appeared to be membrane-bound and required the presence of a detergent, Triton X-100, for solubilization. Rainbow trout and coho salmon enzymatic activity is greater than the human enzyme activity at 15 degrees C.     

Haemoglobins of the shark, Heterodontus portusjacksoni. III. Amino acid sequence of the beta-chain

The amino acid sequence of the beta-chain of the principal haemoglobin from the shark H. portusjacksoni has been determined. The chain has 141 residues, the same as that of mammalian alpha-chains and less than the 146 residues of mammalian beta-chains or the 148 residues of the alpha-chain from the tetrameric shark haemoglobin. The sequence was deduced from the sequences of peptides obtained by digestion of the globin or its cyanogen bromide fragments with trypsin, chymotrypsin, pepsin and papain. The difference in length of the beta-chain is most readily accounted for by the absence of the D helix. This small helical section is normally present in myoglobins and beta-globins but absent in alpha-chains. The deduction that it is absent from shark beta-chain is based on consideration of homology. The beta-chain shows the insertion of histidine beta2 and the deletions corresponding to residues A17 and AB1 relative to alpha-and myoglobin chains. The reactive thiol group in shark haemoglobin was shown by radioactive labelling to be residue 51 in the beta-chain, immediately preceding the E helix. The amino acid sequence of shark beta-chain shows 92 differences from human beta-chain, significantly more differences than shown by chicken or frog beta-chains, in line with its earlier time of divergence. If the tertiary structure of the shark beta-chain is the same as that of the horse then there are two changes in the alpha1beta2 contact site in oxyhaemoglobin and an additional one in deoxyhaemoglobin. When both alpha- and beta-chain contacts are considered there is a total of nine changes in residues involved in the alpha1beta2 contacts. There is no Bohr effect in shark haemoglobin, and of the residues normally involved in this effect the C-terminal histidine residue of the beta-chain is present, but the aspartyl (FG1) residue to which it is salt-linked is not, being replaced by a glutamyl residue.