Amino acid sequences of myosin essential and regulatory light chains from two clam species: comparison with other molluscan myosin light chains.

We have determined the amino acid sequences of the essential light chains (ELC) and regulatory light chains (RLC) of myosin from two species of clam, Mercenaria mercenaria and Macrocallista nimbosa, using protein chemistry methods. The N-termini of all four proteins were blocked, and sequencing was carried out on various chemically and enzymatically produced peptide fragments. Cleavage of either Mercenaria RLC (MRLC) or Macrocallista RLC (VLC) at its 3 Arg yielded four peptides, three of which could not be sequenced directly, due to an N-terminal blocking group and 2 Arg-Gln bonds in these proteins. The fourth peptide was partially and specifically cleaved at an unusually reactive residue, Met-64, which is invariant in all known RLC sequences. A comparison of all available molluscan ELC and RLC sequences was carried out in search of clues to functionally important features of these proteins in muscles which are regulated by a Ca(2+)-sensitive myosin. By analogy with other RLCs, VRLC and MRLC may be phosphorylated at Ser-11 by an endogenous kinase. All myosin light chains, like troponin C and calmodulin, contain four homologous regions, I to IV, each of which contains a twelve-residue potential Ca(2+)-binding loop flanked on either side by a pair of helices. All RLCs, including those from Ca(2+)-insensitive myosins, contain a divalent cation-binding site in region I. Clam and other molluscan ELCs contain a single Ca(2+)-binding site in region III. This site is present only in the ELCs of myosins that are regulated by direct binding of Ca2+. The ELC site III is likely to play a key role in the regulation of molluscan muscle contraction.

Microheterogeneity and interspecific variability of the nuclear sperm proteins from Mytilus.

We have used acetic acid-urea-triton (AUT) gel electrophoresis and ionic exchange chromatography in order to analyze the interspecific variability and microheterogeneity pattern of the protamine-like (PL) proteins of the sperm of 4 different species of the bivalve mollusc, Mytilus. We have found that based upon these 2 criteria, it is possible to unambiguously distinguish each species from the rest. We have thus been able to corroborate the identity of M. trossulus. We have also analyzed the amino acid composition of some of the PL components for each different species. In the case of the PL-II* fraction, we have analyzed the composition of its major protein subcomponents.

Comparison of microwave digestion with conventional wet ashing and dry ashing digestion for analysis of lead, cadmium, chromium, copper, and zinc in shellfish by flame atomic absorption spectroscopy.

A closed vessel microwave digestion procedure was developed for shellfish samples. This procedure was compared with wet and dry ash procedures for levels of lead, cadmium, chromium, copper, and zinc. Results obtained for microwave and conventional wet ash digestion were comparable. The dry ashing procedure produced results consistently lower than either of the other methods. Recoveries ranged from 80-92% for microwave and wet ashing procedures and 54-72% for the dry ashing procedure. Accuracy was also determined by analyzing lobster hepatopancreas marine reference material. Values for Pb, Cd, and Cr fell within the range specified for the reference material for all 3 digestion procedures; however, values were lower for Cu and Zn. Results of this study show that microwave digestion is comparable to wet ashing.

Liquid chromatographic determination of domoic acid in mussels, using AOAC paralytic shellfish poison extraction procedure: collaborative study.

A liquid chromatographic method using the AOAC paralytic shellfish poison (PSP) extraction procedure for domoic acid, a marine toxin, in mussel tissue was collaboratively studied in 10 laboratories. Domoic acid is extracted by boiling the homogenized tissue for 5 min with 0.1N HCl. The mixture is cooled, diluted to a known volume, and then centrifuged. An aliquot of the supernate is diluted, filtered, and analyzed by reverse-phase liquid chromatography with a mobile phase containing acetonitrile and water adjusted to about pH 2.5. Each collaborator received a prepared standard solution, a practice sample, and 7 randomly numbered unknown samples (1 blank mussel tissue, 1 spiked at 14.1 micrograms domoic acid/g, 1 spiked at 18.9 micrograms/g, and duplicate samples with naturally incurred domoic acid at 75 micrograms/g and at 186 micrograms/g). Five of the laboratories had little or no experience in domoic acid analysis. Ten of 11 laboratories completed the study and submitted results. Two individual values out of a total of 70 were found to be outliers. Mean recovery of domoic acid from the spiked extracts was 75%. Relative standard deviations between laboratories (RSDR) ranged from 7.5 to 19.4%; within-laboratory RSDs (RSDr) for the 2 blind duplicate pairs were 1.9 and 4.8%. The detection limit was about 1 microgram domoic acid/g. The method has been adopted official first action by AOAC.

Liquid chromatography-linked protein phosphatase bioassay; a highly sensitive marine bioscreen for okadaic acid and related diarrhetic shellfish toxins.

Okadaic acid and dinophysistoxin-1 were resolved by liquid chromatography, then identified and quantitated by specific inhibition of both protein phosphatase-1 and -2A (PP1/PP2A) catalytic subunits in a 32P-phosphorylase a phosphatase radioassay. Based on the IC50 for PP2A inhibition (0.2 nM), the procedure has a detection sensitivity of less than 10 pg okadaic acid. Confirmative identification by PP1 inhibition (IC50 = 19 nM) requires 500 pg okadaic acid. Analyses of methanolic extracts from control, "okadaic acid spiked" and suspected diarrhetic mussels showed the bioscreen to be accurate, reproducible and identified okadaic acid/dinophysistoxin-1 in Canadian shellfish for the first time. In addition, a protein phosphatase inhibitor distinct from okadaic acid/dinophysistoxin-1 was identified in diarrhetic mussels with a potency equivalent to 900 ng okadaic acid/g digestive tract. Protein phosphatase inhibition probably underlies the biological activity of okadaic acid as a diarrhetic shellfish toxin and tumour promoter (Cohen, P., Holmes, C. F. B. and Tsukitani, Y. (1990), TIBS 15, 98-102). The liquid chromatography-linked protein phosphatase bioscreen should therefore facilitate identification of novel toxins comprising diarrhetic profiles in infested shellfish.

Freshwater mussels as biomonitors for organic industrial contaminants and pesticides in the St. Lawrence River.

Native mussels (Elliptio complanata and Lampsilis radiata radiata) were collected from 17 stations in the St. Lawrence River between Lake Ontario and Trois Rivières and from three stations in a major tributary, the Ottawa River, in October, 1985. Mussels were solvent-extracted and analyzed individually by dual capillary column gas chromatography for seven organochlorine pesticides, 11 chlorobenzenes, octachlorostyrene and 63 PCB congeners. Bioconcentration patterns for contaminants in mussel tissues implicated Lake Ontario as the source of Mirex and DDT derivatives to the system and the Grass River as the major source of PCBs. Numbers of PCB congeners in mussels increased from 21-27 in the upper river to 56-59 in the Cornwall/Massena industrial core, mainly due to the appearance of di-, tri- and tetrachlorobiphenyls; an average of 43 congeners persisted as far downstream as Lac Saint-Pierre. Concentrations of most contaminants in mussels from the Ottawa River were 50-75% lower than the lowest values reported for the St. Lawrence River. This study provides information on the origin, bioavailability and persistence of organic contaminants in the St. Lawrence River ecosystem.

Determination of germanium in some plants and animals.

The Ge contents of plants and animals were investigated by a wet ashing procedure by hydride generation and inductively coupled plasma atomic emission spectrometry with flow injection. The analytical results obtained indicated that Ge contents widely vary in plant and animal kingdoms in the range of 8-302 ppb.

Chemistry, biology, and toxicology of domoic acid and its isomers.

The causative agent of toxicity in cultured mussels from a localized area of eastern Prince Edward Island has been identified as domoic acid, a neuroexcitatory amino acid. The toxin was isolated by a number of different bioassay-directed separation techniques including high-performance liquid chromatography (HPLC), high-voltage paper electrophoresis (HVPE), and ion-exchange chromatography, and characterized by a number of spectroscopic techniques including ultraviolet, infrared, mass spectrometry, and nuclear magnetic resonance. The isolation and purification methods are described in detail and some new analytical data for domoic acid are reported. A plankton bloom at the time of the outbreak gave positive mouse bioassays and consisted almost entirely of the pennate diatom, Nitzschia pungens f. multiseries. A positive correlation was found between the number of N. pungens cells and the concentration of domoic acid in the plankton. N. pungens f. multiseries isolated from Cardigan Bay produced domoic acid de novo during stationary phase culture at levels (1 to 10 pg/cell) comparable to values estimated for N. pungens in the plankton samples. We conclude that N. pungens was the major source of the domoic acid in toxic mussels in eastern Prince Edward Island. The recurrence, in November 1988, of a monospecific bloom of N. pungens and the presence of domoic acid in plankton and mussels reinforces this conclusion.

Mussel culture and the accumulation of domoic acid.

The cultured mussel industry of Prince Edward Island had never experienced a toxic disease problem until November of 1987. With the successful use of the long-line culture system, the yearly production of fresh mussels to the gourmet food market had risen to close to 3.2 million pounds (1.46 million kg) of product. The physiology of this sessile bivalve and its method of feeding and location in the estuary leave it prone to the accumulation of a widely distributed biotoxin. Eastern Prince Edward Island became the epicentre of domoic acid-intoxicated mussels as early as 10 November 1987 (retrospective samples) during an intense bloom of the diatom Nitzschia. Mussels were able to accumulate large amounts of the domoic acid with little effect on their own well-being. Despite being in low water temperatures (below 4 degrees C) and under thick ice cover, the levels of the toxin decreased and were undetectable in about 6 weeks. The following year the toxin was detected in much smaller amounts, and the levels of toxin accumulation demonstrated a variable lag time with the increase in concentration of Nitzschia available in the water column. The sales of Prince Edward Island cultured mussels have rebounded to about 140% of the pre-domoic acid crisis.

Column chromatographic pre-concentration of iron(III) in alloys and biological samples with 1-nitroso-2-naphthol-3,6-disulphonate and benzyldimethyltetradecylammonium-perchlorate adsorbent supported on naphthalene using atomic absorption spectrometry.

The solid ion-pair material produced from the reaction between benzyldimethyltetradecylammonium chloride (BDTA) and sodium perchlorate on naphthalene provides the basis for a simple, rapid and selective technique for pre-concentrating iron from up to 500 ml of aqueous solution. Iron reacts with disodium 1-nitroso-2-naphthol-3,6-disulphonate (Nitroso-R salt) to form a water-soluble coloured chelate anion. The iron chelate anion forms a water-insoluble, stable iron-Nitroso-R-BDTA complex on naphthalene packed in a column. Trace amounts of iron are quantitatively retained on naphthalene in the pH range 3.5-7.5 and at a flow-rate of 1-2 ml min-1. The solid mass is dissolved out from the column with 5 ml of N,N-dimethylformamide and iron is determined by means of an atomic absorption spectrometer at 248 nm. The calibration graph is linear for concentrations of iron over the range of 0.5-20 micrograms in 5 ml of final solution. The standard deviation and relative standard deviation were calculated. The detection limit of the method was 0.0196 micrograms ml-1 of iron. The sensitivity for 1% absorption was 0.072 microgram ml-1 (0.165 microgram ml-1 by direct atomic absorption spectrometry of aqueous solution). The proposed method was applied to the determination of iron in standard alloys and biological samples.

Calcium regulated thin filaments from molluscan catch muscles contain a caldesmon-like regulatory protein.

The thin filaments of the anterior byssus retractor muscle of the edible mussel Mytilus and the transluscent and opaque adductors of the oyster Crassostrea have been isolated and their properties investigated. We find that the thin filaments from all three muscles can activate skeletal muscle myosin ATPase in the presence of calcium but that the activity is inhibited in its absence. The filaments contain a protein which interacts with antibodies to vertebrate smooth muscle caldesmon on immunoblots. The antibodies relieve the inhibition of the thin-filament-activated myosin MgATPase. They can also bundle the thin filaments. We conclude that a caldesmon-like protein is present in molluscan muscle. As in the vertebrate smooth muscle, it could act as part of a control mechanism in addition to the myosin regulatory system. Vertebrate smooth muscle caldesmon can crosslink actin and myosin and it has been suggested that it may in this way contribute to the latch state. A similar interaction may be involved in the catch mechanism in molluscan muscle.

[The problem of selective determination of PSP toxins in mussels]. / Zur Problematik der selektiven Erfassung von PSP-Toxinen aus Muscheln.

Levels of paralytic shellfish poisoning (PSP) toxins in shellfish are routinely determined by mouse bioassay. In order to improve the qualitative and quantitative determination of PSP toxins, chromatographic techniques with fluorescence detection have been developed. These HPLC methods and the HPLC/MS coupling were used to determine a second PSP toxin which was found, in addition to saxitoxin, in canned Spanish mussels. These canned mussels were rejected in 1986 by the German food control because PSP concentrations were too high. It has been shown that these samples contained mainly dc-saxitoxin.

Immunocytochemical localization of a calcium-binding phosphoprotein in hemocytes of heterodont bivalves.

Calcium-binding phosphoprotein particles are the most abundant extracellular proteins in the hemolymph of heterodont bivalves, and granular hemocytes are the most abundant cells in the same fluid. In this study, the hemocytes of Rangia cuneata were examined ultrastructurally and probed with anti-phosphoprotein IgG to demonstrate that the granulocytes are a probable source of the hemolymph phosphoprotein. The granulocyte cytoplasm is laden with large vesicles containing an amorphous homogenous matrix and variable numbers of electron-dense particles; the latter are ultrastructurally similar to the extracellular phosphoprotein. The vesicle particles and matrix are related forms of the hemolymph phosphoprotein as evidenced by heavy gold labeling when Lowicryl sections were sequentially treated with rabbit-anti-phosphoprotein IgG and colloidal gold-anti-rabbit IgG. The vesicles may be the loci for posttranslational phosphorylation and eventual secretion of the calcium-binding phosphoprotein, or alternatively the vesicles may be digestive structures which degrade internalized phosphoprotein.

Protein-based medical adhesives.

There are many naturally occurring adhesive proteins which have potential for application in medicine and dentistry. Cloning and expression of their genes enables the modes of action of these proteins to be better understood and increases their availability for practical applications. This article concentrates on the adhesive protein from the blue mussel Mytilus edulis but also describes medical adhesives based on fibrin isolated from human blood.

Relationship between domoic acid levels in the blue mussel (Mytilus edulis) and toxicity in mice.

Monitoring of eastern blue mussels (Mytilus edulis), contaminated with domoic acid, involved mouse bioassays and quantitative analysis using HPLC. Mice undergo a typical scratching syndrome at sublethal as well as lethal doses of domoic acid. The onset of scratching behaviour and time of death in mice were inversely related to the dosage of domoic acid. An LD50 (i.p.) of 3.6 mg domoic acid/kg mouse was calculated. Toxic mussels held in tanks and flushed with uncontaminated sea water showed a decline in domoic acid concentration in mussel tissue with time. In addition, domoic acid concentrations in mussels from two infected rivers declined to negligible levels in 40-50 days under normal environmental conditions. The bulk of domoic acid and toxicity was located in the hepatopancreas which also contained large amounts of chlorophyll-A, an algae biomass indicator, relative to control mussels. These results support the conclusion that domoic acid was the primary causative factor in the shellfish poisonings from Prince Edward Island mussels in late 1987.

Amino acid sequence of the dimeric hemoglobin (Hb I) from the deep-sea cold-seep clam Calyptogena soyoae and the phylogenetic relationship with other molluscan globins.

The deep-sea cold-seep clam Calyptogena soyoae has two homodimeric hemoglobins (Hbs I and II) in erythrocytes. The complete amino acid sequence of Hb I has been determined. It is composed of 144 amino acid residues, has a high content of hydrophobic residues, and a calculated molecular weight of 16,350 including a heme group. The sequence of Calyptogena Hb I showed high homology (42% identity) with that of Calyptogena Hb II (Suzuki, T., Takagi T. and Ohta, S. (1989) Biochem. J. 260, 177-182), although it has a long insertion of seven residues in the C-terminal region compared with Hb II. On the other hand, it showed low homology (12-20% identity) with other molluscan globins. As well as Hb II, Calyptogena Hb I lacked the N-terminal extension of 7-9 residues characteristic of molluscan intracellular hemoglobins, and the distal (E7) histidine was replaced by glutamine. A phylogenetic tree was constructed from 13 molluscan globins belonging to the five families Aplysiidae, Galeodidae, Potamididae, Arcidae and Vesicomyidae. The globin sequences of Calyptogena (Vesicomyidae) were found to be rather distant from other globin sequences, suggesting that they might conserve a primitive form of molluscan globins.