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PubMed2002

Lethal and sub-lethal effects of chlorination on green mussel Perna viridis in the context of biofouling control in a power plant cooling water system.

Continuous chlorination is a widely followed cooling water treatment practice used in the power industry to combat biofouling. The green mussel Perna viridis is one of the dominant fouling organisms ( > 70%) in the Madras Atomic Power Station. Mortality pattern as well as physiological responses such as oxygen consumption, filtration rate, byssus thread production and faecal matter production of three different size groups of this mussel were studied at different chlorination concentrations. At 0.7 mg l(-1) residual chlorine, 3-4 cm size mussels showed 100% mortality in 553.3 h while 8-9 cm size group mussels died within 588 h. At a relatively high level of residual chlorine (9.1 mg l(-1)), 100% mortality in 3-4 cm and 8-9 cm size groups took 94 and 114 h, respectively. All physiological activities studied showed a progressive reduction as chlorine residuals were increased from 0 to 0.55 mg l(-1). The data indicated that the green mussel can sense a residual chlorine level as low as < 0.15 mg l(-1) and complete valve closure occurs only at 0.55 mg l(-1). The paper also shows that the sub-lethal physiological responses are better indices than lethal responses in planning chlorination strategies.

Adaptation, Physiological↗
PubMed2002

Potent antagonistic action of synthetic analogues of APGWGNamide, an antagonist of molluscan neuropeptide APGWamide.

Fifty-five kinds of analogues of APGWGNamide (Ala-Pro-Gly-Trp-Gly-Asn-NH2), which is an antagonist of molluscan neuropeptide APGWamide, were synthesized and their antagonistic activities were examined on two molluscan smooth muscles. Among all the analogues tested, on spontaneous contraction of the crop of the land snail, Euhadra congenita, APGWG(L-biphenylalanine, Bip)amide showed the most potent antagonistic activity and its potency was 50-100 times higher than that of APGWGNamide. Likewise, on phasic contraction of the anterior byssus retractor muscle (ABRM) of the sea mussel, Mytilus edulis, the effect of APGWG(D-homophenylalanine, dHfe) was the most potent and showed 5-10 times stronger activity than that of APGWGNamide. In the tolerance test to known exo- and endopeptidases or the crop tissue homogenate, APGWGNamide was not only easily degraded by a proline-specific endopeptidase but also by the homogenate. Two kinds of potent antagonists were thus developed: APGWG(Bip)amide and APGWG(dHfe)amide, which will be useful tools for investigation of the function of APGWamide in the snail and the mussel, respectively.

Amino Acid Sequence↗
PubMed2004

Exploring molecular and mechanical gradients in structural bioscaffolds.

Most organisms consist of a functionally adaptive assemblage of hard and soft tissues. Despite the obvious advantages of reinforcing soft protoplasm with a hard scaffold, such composites can lead to tremendous mechanical stresses where the two meet. Although little is known about how nature relieves these stresses, it is generally agreed that fundamental insights about molecular adaptation at hard/soft interfaces could profoundly influence how we think about biomaterials. Based on two noncellular tissues, mussel byssus and polychaete jaws, recent studies suggest that one natural strategy to minimize interfacial stresses between adjoining stiff and soft tissue appears to be the creation of a "fuzzy" boundary, which avoids abrupt changes in mechanical properties. Instead there is a gradual mechanical change that accompanies the transcendence from stiff to soft and vice versa. In byssal threads, the biochemical medium for achieving such a gradual mechanical change involves the elegant use of collagen-based self-assembling block copolymers. There are three distinct diblock copolymer types in which one block is always collagenous, whereas the other can be either elastin-like (soft), amorphous polyglycine (intermediate), or silk-like (stiff). Gradients of these are made by an incrementally titrated expression of the three proteins in secretory cells the titration phenotype of which is linked to their location. Thus, reflecting exactly the composition of each thread, the distal cells secrete primarily the silk- and polyglycine-collagen diblocks, whereas the proximal cells secrete the elastin- and polyglycine-collagen diblocks. Those cells in between exhibit gradations of collagens with silk or elastin blocks. Spontaneous self-assembly appears to be by pH triggered metal binding by histidine (HIS)-rich sequences at both the amino and carboxy termini of the diblocks. In the polychaete jaws, HIS-rich sequences are expanded into a major block domain. Histidine predominates at over 20 mol % near the distal tip and diminishes to about 5 mol % near the proximal base. The abundance of histidine is directly correlated to transition metal content (Zn or Cu) as well as hardness determined by nanoindentation. EXAFS analyses of the jaws indicate that transition metals such as Zn are directly bound to histidine ligands and may serve as cross-linkers.

Animals↗
PubMedDate not supplied

Adhesion of Mytilus edulis foot protein 1 on silica: ionic effects on biofouling.

To determine the effect of the ionic environment on the marine adhesion molecule Mytilus edulis foot protein 1 (Mefp-1), atomic force microscopy (AFM) was used to measure the adhesion between Mefp-1 and a silica substrate under a range of ionic conditions. Both ion strength and type were varied on the basis of the ions present in natural seawater. Salts containing monovalent ions (NaCl, KCl) increased adhesion only slightly, but salts containing divalent ions (MgCl(2), CaCl(2), Na(2)SO(4)) induced multiple jumpouts in the decompression curve similar to other biological systems and an increase in hydrodynamic radius as observed by light scattering. This behavior may be due to metal complexation between 3,4-dihydroxyphenyl-L-alanine and o-quinone catechol groups on Mefp-1. The addition of a salt containing a trivalent ion (FeCl(3)) resulted in the highest adhesion. The strong effect of salt type and concentration suggests that the ionic composition of the environment within the mussel byssus may be tailored in order to achieve maximum adhesion and minimum curing time.

Animals↗
PubMed1997

Phosphorylation of a high molecular weight (approximately 600 kDa) protein regulates catch in invertebrate smooth muscle.

A unique property of smooth muscle is its ability to maintain force with a very low expenditure of energy. This characteristic is highly expressed in molluscan smooth muscles, such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis, during a contractile state called 'catch'. Catch occurs following the initial activation of the muscle, and is characterized by prolonged force maintenance in the face of a low [Ca2+]i, high instantaneous stiffness, a very slow cross-bridge cycling rate, and low ATP usage. In the intact muscle, rapid relaxation (release of catch) is initiated by serotonin, and mediated by an increase in cAMP and activation of protein kinase A. We sought to determine which proteins undergo a change in phosphorylation on a time-course that corresponds to the release of catch in permeabilized ABRM. Only one protein consistently satisfied this criterion. This protein, having a molecular weight of approximately 600 kDa and a molar concentration about 30 times lower than the myosin heavy chain, showed an increase in phosphorylation during the release of catch. Under the mechanical conditions studied (rest, activation, catch, and release of catch), changes in phosphorylation of all other proteins, including myosin light chains, myosin heavy chain and paramyosin, are minimal compared with the cAMP-induced phosphorylation of the approximately 600 kDa protein. Under these conditions, somewhat less than one mole of phosphate is incorporated per mole of approximately 600 kDa protein. Inhibition of A kinase blocked both the cAMP-induced increase in phosphorylation of the protein and the release of catch. In addition, irreversible thiophosphorylation of the protein prevented the development of catch. In intact muscle, the degree of phosphorylation of the protein increases significantly when catch is released with serotonin. In muscles pre-treated with serotonin, a net dephosphorylation of the protein occurs when the muscle is subsequently put into catch. We conclude that the phosphorylation state of the approximately 600 kDa protein regulates catch.

Animals↗
PubMedDate not supplied

Novel materials from protein-polymer grafts.

Proteins are the most underrated and under-used polymers: their impressive properties include infusibility, great mechanical strength and inherent adhesive capability due to a highly flexible backbone and many functional side chains. The notion of moisture sensitivity of proteins is not universally true. Barnacle cement (which can adhere to Teflon) and mussel and clam byssus, all of which are 99% protein, set in the presence of water and resist enzymatic as well as chemical degradation at ambient temperature. This observation suggests that proteins that are capable of tight three-dimensional cross-linking can overcome sensitivity to moisture and enzymatic attack. It should then be possible to achieve similar resistance by appropriate chemical manipulation of proteins, leading to cross-linking. We have achieved such a result with an ordinary protein, commercially available gelatin, which was chemically modified and then epoxidized. When cured such a material binds to metals and plastics. Any protein that has modifiable amino acids can be used for this purpose.

Adhesives↗
PubMed1998

Phosphorylation of a twitchin-related protein controls catch and calcium sensitivity of force production in invertebrate smooth muscle.

"Catch" is a condition of prolonged, high-force maintenance at resting intracellular Ca2+ concentration ([Ca2+]) and very low energy usage, occurring in invertebrate smooth muscles, including the anterior byssus retractor muscle (ABRM) of Mytilus edulis. Relaxation from catch is rapid on serotonergic nerve stimulation in intact muscles and application of cAMP in permeabilized muscles. This release of catch occurs by protein kinase A-mediated phosphorylation of a high (approximately 600 kDa) molecular mass protein, the regulator of catch. Here, we identify the catch-regulating protein as a homologue of the mini-titin, twitchin, based on (i) a partial cDNA of the purified isolated protein showing 77% amino acid sequence identity to the kinase domain of Aplysia californica twitchin; (ii) a polyclonal antibody to a synthetic peptide in this sequence reacting with the phosphorylated catch-regulating protein band from permeabilized ABRM; and (iii) the similarity of the amino acid composition and molecular weight of the protein to twitchin. In permeabilized ABRM, at all but maximum [Ca2+], phosphorylation of twitchin results in a decreased calcium sensitivity of force production (half-maximum at 2.5 vs. 1.3 microM calcium). At a given submaximal force, with equal numbers of force generators, twitchin phosphorylation increased unloaded shortening velocity approximately 2-fold. These data suggest that aspects of the catch state exist not only at resting [Ca2+], but also at higher submaximal [Ca2+]. The mechanism that gives rise to force maintenance in catch probably operates together, to some extent, with that of cycling myosin crossbridges.

Amino Acid Sequence↗
PubMed2003

Twitchin from molluscan catch muscle: primary structure and relationship between site-specific phosphorylation and mechanical function.

The phosphorylation state of the myosin thick filament-associated mini-titin, twitchin, regulates catch force maintenance in molluscan smooth muscle. The full-length cDNA for twitchin from the anterior byssus retractor muscle of the mussel Mytilus was obtained using PCR and 5'rapid amplification of cDNA ends, and its derived amino acid sequence showed a large molecule ( approximately 530 kDa) with a motif arrangement as follows: (Ig)11(IgFn2)2Ig(Fn)3Ig(Fn)2Ig(Fn)3(Ig)2(Fn)2(Ig)2 FnKinase(Ig)4. Other regions of note include a 79-residue sequence between Ig domains 6 and 7 (from the N terminus) in which more than 60% of the residues are Pro, Glu, Val, or Lys and between the 7th and 8th Ig domains, a DFRXXL motif similar to that thought to be necessary for high affinity binding of myosin light chain kinase to F-actin. Two major phosphorylation sites, i.e. D1 and D2, were located in linker regions between Ig domains 7 and 8 and Ig domains 21 and 22, respectively. Correlation of the phosphorylation state of twitchin, using antibodies specific to D1 and D2, with mechanical properties suggested that phosphorylation of both D1 and D2 is required for relaxation from the catch state.

Amino Acid Sequence↗
PubMed1976

Paramyosin in invertebrate muscles. I. Identification and localization.

By sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunodiffusion, we identified paramyosin in two smooth invertebrate "catch" muscles (Mytilus anterior byssus retractor and Mercenaria opaque adductor) and five invertebrate striated muscles (Limulus telson levator, Homarus claw muscle, Balanus scutal depressor, Lethocerus air tube retractor, and Aequipecten striated adductor). We show that (a) the paramyosins in all of these muscles have the same chain weights and (b) they are immunologically similar. We stained all of these muscles with specific antibody to Limulus paramyosin using the indirect fluorescent antibody technique. Paramyosin was localized to the A bands of the glycerinated striated muscles, and diffus fluorescence was seen throughout the glycerinated fibers of the smooth catch muscles. The presence of paramyosin in Homarus claw muscle, Balanus scutal depressor, and Lethocerus air tube retractor is shown here for the first time. Of the muscles in this study, Limulus telson levator is the only one for which the antiparamyosin staining pattern has been previously reported.

Animals↗
PubMed1976

Paramyosin in invertebrate muscles. II. Content in relation to structure and function.

By quantitative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, paramyosin:myosin heavy chain molecular ratios were calculated for three molluscan muscles:Aequipecten striated adductor, Mercenaria opaque adductor, and Mytilus anterior byssus retractor; and four arthropodan muscles:Limulus telson, Homarus slow claw. Balanus scutal depressor, and Lethocerus air tube retractor. These ratios correlate positively with both thick filament dimensions and maximum active tension development in these tissues. The role of paramyosin in these muscles is discussed with respect to the following characteristics: force development, "catch," and extreme reversible changes in length.

Animals↗
PubMed1958

The effect of ions upon the response of smooth muscle to cooling.

The slow tonic responses of the anterior byssus retractor of Mytilus edulis to rapid cooling were investigated by simultaneously recording tension and resting potential changes after soaking the muscle in banthine, a powerful neuromuscular blocking agent. The quantitative relations between the amount of cooling and the amount of associated depolarization necessary for contraction at various concentrations of potentiating potassium can be expressed in a family of curves. The plateaus of the curves for sea water and for potassium-free sea water were beneath the depolarization value necessary for contraction, so that it is clear that no amount of cooling with sea water alone or with potassium-free sea water would ever be effective. When the muscle is treated with subthreshold amounts of potassium and rapidly cooled in various concentrations of sodium ion and calcium ion, respectively, the sodium and calcium do not affect the amount of depolarization. Acetylcholine, in subthreshold amounts, has a potentiating effect, but, unlike potassium and cooling, acts through the nervous apparatus. Mytilus muscle will respond to cooling with tonic contraction whenever a critical threshold amount of depolarization is achieved. Cooling alone cannot trigger the contraction since it cannot bring about sufficient depolarization. Cooling can result in contraction, however, if used in conjunction with some other subthreshold depolarizing agent. Cooling affects the contractile mechanism by first causing membrane breakdown and depolarization.

Acetylcholine↗
PubMed1962

Water loss during contracture of muscle.

The relationship of contracture and exudation of water in frozenthawed frog muscle was studied. With maximum shortening, there was a water loss of 35 per cent of the weight of muscle. By restricting the contraction, it was demonstrated that the amount of water loss was proportional to the degree of shortening, there being no significant loss with isometric contraction. Muscle already shortened by tetanic stimulation also exuded water on subsequent freezing and thawing. The force of contraction could be reduced by depleting the muscle of calcium and it was shown that the amount of water exuded was also proportional to the tensile ability of the muscle. In a smooth muscle (anterior byssus retractor of Mytilus) which did not contract vigorously only a little water exuded. Contracture produced by caffeine was similarly associated with a loss of water. Microscopic studies revealed a disruption of the sarcomeres of the frozen-thawed muscle which contracted; glycerol-extracted and calcium-depleted muscles, which did not contract on freeze-thawing, did not show such disruption. Freezing and thawing of actomyosin caused a reversible syneresis of the protein. It is concluded that the exudation of the water is not merely due to the freezing and thawing but is also dependent on the contractile events.

Actin Cytoskeleton↗
PubMed1973

The structure of Mytilus smooth muscle and the electrical constants of the resting muscle.

The individual muscle fibers of the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. are uninucleate, 1.2-1.8 mm in length, 5 microm in diameter, and organized into bundles 100-200 microm in diameter, surrounded by connective tissue. Some bundles run the length of the whole muscle. Adjacent muscle cell membranes are interconnected by nexuses at frequent intervals. Specialized attachments exist between muscle fibers and connective tissue. Electrical constants of the resting muscle membrane were measured with intracellular recording electrodes and both extracellular and intracellular current-passing electrodes. With an intracellular current-passing electrode, the time constant tau, was 4.3 +/- 1.5 ms. With current delivered via an extracellular electrode tau was 68.3 +/- 15 ms. The space constant, lambda, was 1.8 mm +/- 0.4. The membrane input resistance, R(eff), ranged from 23 to 51 MOmega. The observations that values of tau depend on the method of passing current, and that the value of lambda is large relative to fiber length and diameter are considered evidence that the individual muscle fibers are electrically interconnected within bundles in a three-dimensional network. Estimations are made of the membrane resistance, R(m), to compare the values to fast and slow striated muscle fibers and mammalian smooth muscles. The implications of this study in reinterpreting previous mechanical and electrical studies are discussed.

Animals↗
PubMed1980

The regulation of tension in a chemically skinned molluscan smooth muscle: effect of Mg2+ on the Ca2+-activated tension generation.

Chemically skinned anterior byssus retractor muscle (ABRM) preparations were prepared by treatment with the nonionic detergents saponin and Triton X-100. Both maximum peak tension and rate of contraction were found to be greater in saponin-treated ABRM than in ABRM treated with Triton X-100. Active tension was initiated at a concentration of free Ca2+ above 0.1 microM, and maximum tension development was found at a [Ca2+] = approximately 32 microM. During exposure of the muscle preparation to optimal Ca2+ concentration, a high and almost constant tension level was sustained. The force recovery was high after a quick release during this period indicating the presence of an "active" state rather than a "catch" state. Actually, a state equivalent to the catch state in the living ABRM could not be induced, if the Ca2+ concentration was above 0.1 microM. Variations in the ionic strength in the range of 0.07--0.28 M had no influence on active state and only slightly affected the maximum tension developed. The influence of Mg2+ on the Ca2+-activated tension was examined by studying the tension-pCa relation at two concentrations of free Mg2+ (0.43 and 4.0 mM). The tension-pCa relation was found to be S-shaped with tension increasing steeply over approximately 1 pCa unit, indicating the existence of cooperativity between Ca2+ sites. Increasing the free concentration of Mg2+ shifted the tension-pCa relation to lower pCa as in striated muscles, demonstrating a decreasing Ca2+ sensitivity with increasing Mg2+. At [Mg2+] = 4.0 mM the half-maximum tension was found at [Ca2+] = 0.43 microM, decreasing to 0.20 microM at [Mg2+] = 0.43 mM. At both Mg2+ concentrations studied, plots of log Prel/(1--Prel) vs. log [Ca2+] were nonlinear with a shape indicating a rather complicated model for cooperativity, probably involving four sites for Ca2+. These Ca2+--Mg2+ interactions are most probably taking place at the myosin head itself because troponin is absent in this myosin-regulated muscle.

Adenosine Triphosphate↗
PubMed1982

Tonic contraction and the control of relaxation in a chemically skinned molluscan smooth muscle.

The same functional states that characterize the living anterior byssus retractor muscle (ABRM) from Mytilus edulis can be initiated in the saponin-treated (chemically skinned) muscle preparation under controlled biochemical conditions. A tonic contraction was induced if the concentration of free Ca2+ was above approximately 10(7) M in the presence of Mg2+ and ATP. Maximum tension development was achieved at a Ca2+ concentration of approximately 10(4) M. Within these Ca2+ concentrations tension was always associated with the presence of 'active state," as indicated by a high recovery of tension after a quick release in muscle length. Tonic tension, and the associated active state was maintained for hours during these conditions irrespective of variations in both ionic strength and pH. Reduction of the Ca2+ concentration to below threshold for tension initiation during a tonic contraction immediately switched off the active state and relaxation of the muscle preparation resulted. However, the rate of relaxation was extremely low, leaving a substantial fraction of tension in the absence of active state. Both 5-hydroxytryptamine (5-HT) and cAMP accelerated this slow relaxation in the absence of Ca2+. Thus, this state was considered equivalent to the 'catch state" in the living ABRM. In the presence of Ca2+ concentrations above 10(7) M, cAMP did not affect either the maximum tension developed or the Ca2+ sensitivity of the chemically skinned muscle preparation.

Animals↗
PubMed1992

Sudden increase in speed of an actin filament moving on myosin cross-bridges of "mismatched" polarity observed when its leading end begins to interact with cross-bridges of "matched" polarity.

Under in vitro movement assay conditions, actin filaments move about 10 times faster toward, than away from, the center of large bipolar thick filaments of molluscan smooth muscle. Using thick filaments isolated from the anterior byssus retractor muscle of Mytilus edulis, the two speed modes of movement were studied in detail. Some thick filaments crossed over each other on the surface of the assay chamber, allowing actin filaments that moved into the crossover region to transfer to other thick filaments. When an actin filament that had been moving in the low speed mode crossed over to another thick filament and the speed changed to fast, the entire actin filament started to move in the high speed mode at the moment of transfer of its leading end, leaving the trailing part still in contact with the original thick filament. This indicates that myosin cross-bridges interacting in the slow mode do not impose a significant load on the cross-bridges interacting in the fast mode. Assuming the theoretical model of Tawada and Sekimoto [Biophys. J. 59, 343-356 (1991)], we suggest that the magnitude of force developed, as well as the speed of unloaded movement, differs greatly, depending on the orientation of the myosin cross-bridges.

Actins↗
PubMed2002

Elastic proteins: biological roles and mechanical properties.

The term 'elastic protein' applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is 'stretchy', or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber-like proteins (e.g. resilin and elastin) that function in the storage of elastic-strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology.

Animals↗
PubMed1986

31P-nuclear-magnetic-resonance study of muscles from Mytilus edulis.

Phosphorus-31 nuclear magnetic resonance (NMR) spectra were recorded from freshly excised and resting anterior byssus retractor muscles of the mussel Mytilus edulis. The absolute concentrations of phosphometabolites measured by NMR compare well with the values obtained by a biochemical method. Quantitative measurements were achieved in several minutes by applying to the observed NMR signals a correction taking the saturation effects into account. The time evolution of the phosphometabolite concentrations reveals that the hydrolysis of phosphoarginine is a first-order reaction producing inorganic phosphate, whilst the adenosine triphosphate level remains constant for more than 10 h. The phosphoarginine hydrolysis rate varies as a function of the season and reaches a maximum during the reproduction period of the mussel. This increase in phosphoarginine consumption could be bound up with the higher excitability of the muscles during spring. The activation energy of the phosphoarginine hydrolysis reaction also depends on the season and the difference between the value determined in winter and that measured in spring is explained by a modification of the mode of action or of the proportions of the enzymes involved in the muscular metabolism.

Adenosine Triphosphate↗