Myosin light chain of shark fast skeletal muscle exhibits intrinsic urea-resistibility.

Marine elasmobranch fish contain urea, a protein denaturant, in their bodies. The urea-trimethylamine N-oxide (TMAO) counteraction mechanism contributes to urea-resistibility, where TMAO compensates for protein denaturation by urea. However, previous studies revealed that shark fast skeletal muscle myosin exhibits native activity at physiological urea concentrations in the absence of TMAO, suggesting that shark myosin has urea-resistibility.

Electroextraction of Insoluble Proteins from the Organic Matrix of the Nacreous Layer of the Japanese Pearl Oyster, .

The nacreous layer of shells and pearls is composed of aragonite crystals arranged in an organic matrix. The organic matrix contains chitin and several proteins that regulate the formation of the nacreous layer. Owing to their strong interactions in the organic matrix, the current method for extraction of insoluble proteins from the pre-powdered nacreous layer involves heating to high temperatures in the presence of a detergent (e.

Comparison of Two Pearl Sacs Formed in the Same Recipient Oyster with Different Genetic Background Involved in Yellow Pigmentation in Pinctada fucata.

Color is one of the most important factors determining the commercial value of pearls. Pinctada fucata is a well-known pearl oyster producing high-quality Akoya pearls. Phenotypic variation in amount of yellow pigmentation produces white and yellowish pearls.

Novel Isoforms of N16 and N19 Families Implicated for the Nacreous Layer Formation in the Pearl Oyster Pinctada fucata.

Although a wide variety of proteins and genes possibly related to the shell formation in bivalve have been identified, their functions have been only partially approved. We have recently performed deep sequencing of expressed sequence tags (ESTs) from the pearl oyster Pinctada fucata using a next-generation sequencer, identifying a dozen of novel gene candidates which are possibly associated with the nacreous layer formation. Among the ESTs, we focused on three novel isoforms (N16-6, N16-7, and N19-2) of N16 and N19 families with reference to five known genes in the families and determined the full-length cDNA sequences of these isoforms.

Novel genes participating in the formation of prismatic and nacreous layers in the pearl oyster as revealed by their tissue distribution and RNA interference knockdown.

In our previous publication, we identified novel gene candidates involved in shell formation by EST analyses of the nacreous and prismatic layer-forming tissues in the pearl oyster Pinctada fucata. In the present study, 14 of those genes, including two known genes, were selected and further examined for their involvement in shell formation using the RNA interference. Molecular characterization based on the deduced amino acid sequences showed that seven of the novel genes encode secretory proteins.

Genome-wide survey of genes encoding muscle proteins in the pearl oyster, Pinctada fucata.

The mechanisms of contraction of molluscan striated and smooth muscles differ from those in vertebrates. Molluscan striated muscles adopt a myosin-linked regulation, unlike vertebrates. Smooth muscles in these species show a unique form of contraction, in which the tension is maintained for a long time with little energy consumption, called catch.

Myosin loop 2 is involved in the formation of a trimeric complex of twitchin, actin, and myosin.

Molluscan smooth muscles exhibit a low energy cost contraction called catch. Catch is regulated by twitchin phosphorylation and dephosphorylation. Recently, we found that the D2 fragment of twitchin containing the D2 site (Ser-4316) and flanking immunoglobulin motifs (TWD2-S) formed a heterotrimeric complex with myosin and with actin in the region that interacts with myosin loop 2 (Funabara, D.

The occurrence of tissue-specific twitchin isoforms in the mussel Mytilus galloprovincialis.

The catch state in Mytilus anterior byssus retractor muscle is regulated by phosphorylation and dephosphorylation of twitchin, a member of the titin/connectin superfamily, and involves two serine residues, Ser-1075 (D1) and Ser-4316 (D2). This study was undertaken to examine whether isoforms of twitchin were expressed in various muscles of the mussel Mytilus galloprovincialis by reverse transcription-polymerase chain reaction. Mussel tissues, including both catch and non-catch muscles, contained various twitchin isoforms that all contained the D2 site and the kinase domain.

Unphosphorylated twitchin forms a complex with actin and myosin that may contribute to tension maintenance in catch.

Molluscan smooth muscle can maintain tension over extended periods with little energy expenditure, a process termed catch. Catch is thought to be regulated by phosphorylation of a thick filament protein, twitchin, and involves two phosphorylation sites, D1 and D2, close to the N and C termini, respectively. This study was initiated to investigate the role of the D2 site and its phosphorylation in the catch mechanism.

Twitchin as a regulator of catch contraction in molluscan smooth muscle.

Molluscan catch muscle can maintain tension for a long time with little energy consumption. This unique phenomenon is regulated by phosphorylation and dephosphorylation of twitchin, a member of the titin/connectin family. The catch state is induced by a decrease of intracellular Ca2+ after the active contraction and is terminated by the phosphorylation of twitchin by the cAMP-dependent protein kinase (PKA).

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.