Structural differences in the crossbridge head of temperature-associated myosin subfragment-1 isoforms from carp fast skeletal muscle

Molecular Localization of Health-Promoting Peptides Derived from Fish Protein Hydrolyzates on Fish Muscle Proteins

The four previously reported health-promoting dipeptides, valine-tyrosine, lysine-tryptophan, methionine-phenylalanine, and arginine-isoleucine, found in the fish muscle hydrolyzates, were mainly located in the myosin subfragment-1 heavy chain, whereas the health-promoting tripeptide, alanine-lysine-lysine, was found in the fibrous rod consisting of the myosin subfragment-2 and light meromyosin with a regular coiled-coil structure of α-helix, irrespective of the fish species. Furthermore, the localization of these peptides either in the random coil, β-sheet, or α-helix was also examined in the three-dimensional image, showing no specific tendency. Surprisingly, the same trend was observed even for the mammalian rabbit fast muscle myosin heavy chain. Since a trade-off between myofibrillar ATPase and structural stability has been reported for fish living at low environmental temperatures, it is speculated that fish muscle proteins, when ingested, are easily digested by various proteases in the human digestive tract and provide various health-promoting peptides also in vivo. While fish actin contained only two dipeptides, methionine-phenylalanine and valine-tyrosine, glyceraldehyde 3-phosphate dehydrogenase, one of the major components of fish muscle water-soluble protein, contained all of the four dipeptides and one tripeptide mentioned above.

Comparative analysis of the transcriptome of the Amazonian fish species Colossoma macropomum (tambaqui) and hybrid tambacu by next generation sequencing

Background

The C. macropomum is a characiform fish from the Amazon basin that has been hybridized with other pacu species to produce commercial hybrids, such as the tambacu. However, little is known of the functional genomics of the parental species or these hybrid forms. The transcriptome of C. macropomum and tambacu were sequenced using 454 Roche platform (pyrosequencing) techniques to characterize the domains of Gene Ontology (GO) and to evaluate the levels of gene expression in the two organisms.

Results

The 8,188,945 reads were assembled into 400,845 contigs. A total of 58,322 contigs were annotated with a predominance of biological processes for both organisms, as determined by Gene Ontology (GO). Similar numbers of metabolic pathways were identified in both the C. macropomum and the tambacu, with the metabolism category presenting the largest number of transcripts. The BUSCO analysis indicated that our assembly was more than 40% complete. We identified 21,986 genes for the two fishes. The P and Log2FC values indicated significant differences in the levels of gene expression, with a total of 600 up-regulated genes.

Conclusion

In spite of the lack of a reference genome, the functional annotation was successful, and confirmed a considerable difference in the specificity and levels of gene expression between the two organisms. This report provides a comprehensive baseline for the genetic management of these commercially important fishes, in particular for the identification of specific genes that may represent markers involved in the immunity, growth, and fertility of these organisms, with potential practical applications in aquaculture management.

Mutations in the SH1 helix alter the thermal properties of myosin II

The myosin II SH1 helix is a joint that links the converter subdomain to the rest of the myosin motor domain and possibly plays a key role in the arrangement of the converter/lever arm. Several point mutations within the SH1 helix in human myosin IIs have been shown to cause diseases. To reveal whether these SH1 helix mutations affect not only motile activities but also thermal properties of myosin II, here we introduced the E683K or R686C point mutation into the SH1 helix in Dictyostelium myosin II. Thermal inactivation as well as thermal aggregation rates of these mutant proteins demonstrated that these mutations decreased the thermal stability of myosin II. Temperature dependence of sliding velocities of actin filaments showed that these mutations also reduced the activation energy of a rate-limiting process involved in actin movement. Given that these mutations are likely to alter coupling between the subdomains, and thus their thermal fluctuations, we propose that the SH1 helix is a key structural element that determines the flexibility and thermal properties of the myosin motor. These characteristics of the SH1 helix may contribute to the pathogenesis of the human diseases caused by mutations within this structural element.

Stimulatory and inhibitory mechanisms of slow muscle-specific myosin heavy chain gene expression in fish: transient and transgenic analysis of torafugu MYH(M86-2) promoter in zebrafish embryos

The myosin heavy chain gene, MYHM86-2, exhibited restricted expression in slow muscle fibers of torafugu embryos and larvae, suggesting its functional roles for embryonic and larval muscle development. However, the transcriptional mechanisms involved in its expression are still ambiguous. The present study is the first extensive analysis of slow muscle-specific MYHM86-2 promoter in fish for identifying the cis-elements that are crucial for its expression. Combining both transient transfection and transgenic approaches, we demonstrated that the 2614bp 5'-flanking sequences of MYHM86-2 contain a sufficient promoter activity to drive gene expression specific to superficial slow muscle fibers. By cyclopamine treatment, we also demonstrated that the differentiation of such superficial slow muscle fibers depends on hedgehog signaling activity. The deletion analyses defined an upstream fragment necessary for repressing ectopic MYHM86-2 expression in the fast muscle fibers. The transcriptional mechanism that prevents MYHM86-2 expression in the fast muscle fibers is mediated through Sox6 binding elements. We also demonstrated that Sox6 may function as a transcriptional repressor of MYHM86-2 expression. We further discovered that nuclear factor of activated T cells (NFAT) binding elements plays a key role and myocyte enhancer factor-2 (MEF2) binding elements participate in the transcriptional regulation of MYHM86-2 expression.

Effect of Seasons on Volatile Compounds in Grass Carp Meat

In this paper, the volatile compounds of the belly meat and red meat of cultured grass carp in different seasons were identified by SPME(solid phase micro-extraction)-GC (gas chromatography)-MS (mass spectrometry). The results showed that SPME was effective to analysis of the volatiles in grass carp meat. According to GC-MS, 26, 44, 41 and 26 volatile compounds were detected in belly meat of grass carp in spring, summer, autumn and winter respectively; 48, 46, 43 and 53 volatile compounds were detected in red meat of grass carp in spring, summer, autumn and winter respectively. The volatile components are mostly carbonyl compounds and alcohols, the respective relative contents are above 90%. The relative content of the volatile compounds of cultured grass carp in different seasons has the significance difference by ANOVA. Seasons have great effect on the volatile compounds of grass carp meat and the impact on red meat is smaller than belly meat The study will enrich the theoretical knowledge of flavor chemistry and provide an effective solution to the current situation of low proportion of fish processing.

Multiple cis-elements in the 5'-flanking region of embryonic/larval fast-type of the myosin heavy chain gene of torafugu, MYH(M743-2), function in the transcriptional regulation of its expression

The myosin heavy chain gene, MYH(M743-2), is highly expressed in fast muscle fibers of torafugu embryos and larvae, suggesting its functional roles for embryonic and larval muscle development. However, the transcriptional regulatory mechanism involved in its expression remained unknown. Here, we analyzed the 2075bp 5'-flanking region of torafugu MYH(M743-2) to examine the spatial and temporal regulation by using transgenic and transient expression techniques in zebrafish embryos. Combining both transient and transgenic analyses, we demonstrated that the 2075bp 5'-flanking sequences was sufficient for its expression in skeletal, craniofacial and pectoral fin muscles. The immunohistochemical observation revealed that the zebrafish larvae from the stable transgenic line consistently expressed enhanced green fluorescent protein (EGFP) in fast muscle fibers. Promoter deletion analyses demonstrated that the minimum 468bp promoter region could direct MYH(M743-2) expression in zebrafish larvae. We discovered that the serum response factor (SRF)-like binding sites are required for promoting MYH(M743-2) expression and myoblast determining factor (MyoD) and myocyte enhancer factor-2 (MEF2) binding sites participate in the transcriptional control of MYH(M743-2) expression in fast skeletal muscles. We further discovered that MyoD binding sites, but not MEF2, participate in the transcriptional regulation of MYH(M743-2) expression in pectoral fin and craniofacial muscles. These results clearly demonstrated that multiple cis-elements in the 5'-flanking region of MYH(M743-2) function in the transcriptional control of its expression.

Characterisation of myosin heavy chain gene variants in the fast and slow muscle fibres of gammarid amphipods

Recent molecular work has revealed a large diversity of myosin heavy chain (MyHC) gene variants in the abdominal musculature of gammarid amphipods. An unusual truncated MyHC transcript from the loop 1 region (Variant A(3)) was consistently observed in multiple species and populations. The current study aimed to determine whether this MyHC variant is specific to a particular muscle fibre type, as a change in net charge to the loop 1 region of Variant A(3) could be functionally significant. The localisation of different fibre types within the abdominal musculature of several gammarid species revealed that the deep flexor and extensor muscles are fast-twitch muscle fibres. The dorsal superficial muscles were identified as slow fibres and the muscles extrinsic to the pleopods were identified as intermediate fibres. Amplification of loop 1 region mRNA from isolated superficial extensor and deep flexor muscles, and subsequent liquid chromatography and sequence analysis revealed that Variant A(3) was the primary MyHC variant in slow muscles, and the conserved A(1) sequence was the primary variant in fast muscles. The specific role of Variant A(3) in the slow muscles remains to be investigated.

Early development of medaka Oryzias latipes muscles as revealed by transgenic approaches using embryonic and larval types of myosin heavy chain genes

We cloned three full-length cDNAs encoding myosin heavy chains (MYHs) previously found to be expressed in embryos or larvae of medaka Oryzias latipes. Based on cDNA sequence information, the three medaka MYH genes, mMYH(emb1), mMYH(L1) and mMYH(L2), were localized on the chromosomes. In vivo promoter assay using the gene encoding green or red fluorescent protein and linked to the 5'-flanking region of mMYH demonstrated that the transcripts of fast-type mMYH(emb1), first expressed in embryos but belonging to the adult type in phylogenetic analysis, were located in the horizontal myoseptum. On the other hand, embryonic fast-type mMYH(L1) and mMYH(L2) were expressed in the whole myotomes. Interestingly, cells expressing mMYH(emb1) were localized together with engrailed, and cyclopamine, which blocks hedgehog signaling, inhibited mMYH(emb1) expression as well as the formation of the horizontal myoseptum, suggesting that muscle pioneer cells express mMYH(emb1) as a key protein in the formation of the horizontal myoseptum.

A 5'-flanking region of embryonic-type myosin heavy chain gene, MYH(M)₇₄₃₋₂, from torafugu Takifugu rubripes regulates developmental muscle-specific expression

The myosin heavy chain gene, MYH(M)₇₄₃₋₂, is highly expressed in fast muscle fibers of torafugu embryos. However, the regulatory mechanisms involved in its expression have been unclear. In this study, we examined spatio-temporal expression patterns of this gene during development by injecting expression vectors containing the GFP reporter gene fused to the 5'-flanking region of MYH(M)₇₄₃₋₂ into fertilized eggs of zebrafish and medaka. Although the -2.1kb 5'-flanking region of torafugu MYH(M)₇₄₃₋₂ showed no homology with the corresponding regions of zebrafish and medaka orthologous genes on the rVISTA analysis, the torafugu 5'-flanking region activated the GFP expression which was detected in the myotomal compartment for both zebrafish and medaka embryos. The GFP expression was localized to fast and slow muscle fibers in larvae as revealed by immunohistochemical analysis. In addition to the above tissues, GFP was also expressed in jaw, eye and pectoral fin muscles in embryos and larvae. These results clearly demonstrated that the 2.1 kb 5'-flanking region of MYH(M)₇₄₃₋₂ contains essential cis-regulatory sequences for myogenesis that are conserved among torafugu, zebrafish and medaka.

Fibre type-specific expression patterns of myosin heavy chain genes in adult torafugu Takifugu rubripes muscles

Comprehensive in silico studies, based on the total fugu genome database, which was the first to appear in fish, revealed that torafugu Takifugu rubripes contains 20 sarcomeric myosin heavy chain (MYH) genes (MYH genes) (Ikeda et al., 2007). The present study was undertaken to identify MYH genes that would be expressed in adult muscles. In total, seven MYH genes were found by screening cDNA clone libraries constructed from fast, slow and cardiac muscles. Three MYH genes, fast-type MYH(M86-1), slow-type MYH(M8248) and slow/cardiac-type MYH(M880), were cloned exclusively from fast, slow and cardiac muscles, respectively. Northern blot hybridization substantiated their specific expression, with the exception of MYH(M880). In contrast, transcripts of fast-type MYH(M2528-1) and MYH(M1034) were found in both fast and slow muscles as revealed by cDNA clone library and northern blot techniques. This result was supported by in situ hybridization analysis using specific RNA probes, where transcripts of fast-type MYH(M2528-1) were expressed in fast fibres with small diameters as well as in fibres of superficial slow muscle with large diameters adjacent to fast muscle. Transcripts of fast-type MYH(M86-1) were expressed in all fast fibres with different diameters, whereas transcripts of slow-type MYH(M8248) were restricted to fibres with small diameters located in a superficial part of slow muscle. Interestingly, histochemical analyses showed that fast fibres with small diameters and slow fibres with large diameters both contained acid-stable myofibrillar ATPase, suggesting that these fibres have similar functions, possibly in the generation of muscle fibres irrespective of their fibre types.

Three embryonic myosin heavy chain genes encoding different motor domain structures from common carp show distinct expression patterns in cranial muscles

Three embryonic myosin heavy chain (MYH) genes >> (MYHs) including MYH(emb1), MYH(emb2) and MYH(emb3) and encoding a C-terminal part of MYH were previously cloned and demonstrated to be expressed transiently in this order during development of common carp Cyprinus carpio embryos. The present study determined the full-length cDNA nucleotide sequences encoding the motor domain of the three MYHs, suggesting the implication of loop 1 and loop 2 sequences for the differences in the motor functions. Phylogenetic analysis based on the full-length amino acid sequences showed that MYH(emb1) and MYH(emb2) both belong to the fast types, though clearly differ from fast-type MYHs expressed in adult fast muscle previously reported. In contrast, MYH(emb3) was in a clade containing slow/cardiac type. Whole-mount immunostaining and in situ hybridization showed that the transcripts of the three embryonic MYHs are localized in the same or different cranial muscles of common carp larvae, suggesting that the three MYHs function cooperatively or individually in various cranial muscles.

Structural differences in the motor domain of temperature-associated myosin heavy chain isoforms from grass carp fast skeletal muscle

We determined coding sequences for three types of grass carp myosin subfragment-1 (S1) heavy chain by extending 5'-regions of the three known genes encoding light meromyosin isoforms (10 degrees C, intermediate and 30 degrees C types). The primary structures of these three S1 heavy chain isoforms showed 81.4%, 81.2%, and 97.8% identities between the 10 degrees C and intermediate types, between the 10 degrees C and 30 degrees C types, and between the intermediate and 30 degrees C types, respectively. Isoform-specific differences were clearly observed between the 10 degrees C type and the other two types in 97 amino acid residues. Furthermore, among these amino acid mutations, 51 mutations occurred at the conserved residue sites of S1 heavy chain from fish and homoiotherm. Additionally, the 10 degrees C type showed striking differences compared with the other two types in the two surface loops, loop 1 located near the ATP-binding pocket and loop 2, which is one of the actin-binding sites, suggesting that such structural differences possibly affect their motor functions. Interestingly, this 10 degrees C-type myosin heavy chain isolated from adult grass carp skeletal muscle was surprisingly similar to the embryonic fast-type myosin heavy chain from juvenile silver carp in the structure of S1 heavy chain, indicating that it may also function as embryonic fast-type myosin heavy chain in juvenile stage.

cDNA cloning and characterization of temperature-acclimation-associated light meromyosins from grass carp fast skeletal muscle

The three types of cDNA clones, previously defined as the 10 degrees C, intermediate and 30 degrees C-types [Tao, Y., Kobayashi, M., Liang, C.S., Okamoto, T., Watabe, S., 2004. Temperature-dependent expression patterns of grass carp fast skeletal myosin heavy chain genes. Comp. Biochem. Physiol. B 139, 649-656], were determined for their 5'-regions which encoded at least the C-terminal half of myosin rod, light meromyosin (LMM), in fast skeletal muscles of grass carp Ctenopharyngodon idella. The deduced amino acid sequence identity was 91.1% between the 10 degrees C and 30 degrees C-types and 91.4% between the 10 degrees C and intermediate-types, whereas a high sequence identity of 97.8% was found between the intermediate and 30 degrees C-types. These three grass carp LMMs all had a characteristic seven-residue (heptad) repeat (a, b, c, d, e, f, g)(n), where positions a and d were normally occupied by hydrophobic residues, and positions b, c and f by charged residues. However, the ratios of hydrophobic residues to the total were higher for the intermediate- and 30 degrees C- than 10 degrees C-type LMM, suggesting that the former both types may form more stable coiled-coils of alpha-helices than the latter type. These differences in the primary structures of LMM isoforms might be partially implicated in differences in the thermostabilities and gel-forming profiles of myosins from grass carp in different seasons reported previously [Tao, Y., Kobayashi, M., Fukushima, H., Watabe, S., 2005. Changes in enzymatic and structural properties of grass carp fast skeletal myosin induced by the laboratory-conditioned thermal acclimation and seasonal acclimatization. Fish. Sci. 71, 195-204; Tao, Y., Kobayashi, M., Fukushima, H., Watabe, S., 2007. Changes in rheological properties of grass carp fast skeletal myosin induced by seasonal acclimatization. Fish. Sci. 73, 189-196].

Divergent evolution of the myosin heavy chain gene family in fish and tetrapods: evidence from comparative genomic analysis

Myosin heavy chain genes (MYHs) are the most important functional domains of myosins, which are highly conserved throughout evolution. The human genome contains 15 MYHs, whereas the corresponding number in teleost appears to be much higher. Although teleosts comprise more than one-half of all vertebrate species, our knowledge of MYHs in teleosts is rather limited. A comprehensive analysis of the torafugu (Takifugu rubripes) genome database enabled us to detect at least 28 MYHs, almost twice as many as in humans. RT-PCR revealed that at least 16 torafugu MYH representatives (5 fast skeletal, 3 cardiac, 2 slow skeletal, 1 superfast, 2 smooth, and 3 nonmuscle types) are actually transcribed. Among these, MYH(M743-2) and MYH(M5) of fast and slow skeletal types, respectively, are expressed during development of torafugu embryos. Syntenic analysis reveals that torafugu fast skeletal MYHs are distributed across five genomic regions, three of which form clusters. Interestingly, while human fast skeletal MYHs form one cluster, its syntenic region in torafugu is duplicated, although each locus contains just a single MYH in torafugu. The results of the syntenic analysis were further confirmed by corresponding analysis of MYHs based on databases from Tetraodon, zebrafish, and medaka genomes. Phylogenetic analysis suggests that fast skeletal MYHs evolved independently in teleosts and tetrapods after fast skeletal MYHs had diverged from four ancestral MYHs.

Fast skeletal muscle myosin heavy chain gene cluster of medaka Oryzias latipes enrolled in temperature adaptation

To disclose mechanisms involved in temperature acclimation of fish muscle, we subjected eurythermal fish of medaka Oryzias latipes to cloning of myosin heavy chain genes (MYHs). We cloned cDNAs encoding fast skeletal muscle myosin heavy chain (MYH) isoforms from cDNA libraries of medaka acclimated to 10 and 30 degrees C and observed that different MYH cDNA clones are expressed in the two temperature-acclimated fish. Subsequently, we isolated several overlapping MYH contigs by shotgun cloning strategy from a medaka genomic library. Contig assembly of the complete medaka MYH (mMYH) locus of 219 kbp revealed a cluster of tandemly arrayed 11 mMYHs, in which eight genes are actually transcribed, with the remaining three being pseudogenes. Expression analysis of the transcribed genes revealed that two genes were each highly expressed in medaka acclimated to 10 and 30 degrees C, whereas comparatively lower expression levels of the three genes were exclusively observed in medaka acclimated to 30 degrees C. cDNAs of the remaining genes were too underrepresented in the libraries to determine the expression levels, and the transcripts could only be obtained by reverse transcription-polymerase chain reaction. Deduced amino acid sequences in the loop 1 and loop 2 regions of mMYHs were highly variable, suggesting that these isoforms were functionally different. The present findings consolidate our knowledge on teleost MYH multigene family and would provide further insight into the mechanisms by which expressions of individual MYH molecules are fine-tuned with environmental temperature fluctuations with further functional analysis of the genes concerned.

cDNA cloning of myosin heavy chain genes from medaka Oryzias latipes embryos and larvae and their expression patterns during development

Several sarcomeric myosin heavy chains (MYHs) were cloned from embryos and larvae of medaka Oryzias latipes. Three genes encoding medaka MYHs (mMYHs) predominantly expressed in embryos (mMYH(emb1)) and larvae (mMYH(L1) and mMYH(L2)), all belonged to fast skeletal MYHs, showing spatiotemporally different expression patterns during development. Besides these mMYHs, a few novel mMYHs were cloned from embryos and larvae at hatching. Whereas mMYH(emb2), mMYH(emb3), and mMYH(L3) belonged to fast skeletal MYH, mMYH(C1) and mMYH(C2) did to slow/cardiac MYH. mMYH(emb1) was expressed ahead of mMYH(L1) and mMYH(L2). In situ hybridization analysis demonstrated that the transcripts of mMYH(emb1) and mMYH(C1) were located in the horizontal myoseptum, whereas those of mMYH(L1) and mMYH(L2) in the inner part of myotomes and pharyngeal muscles, and those of mMYH(C2) in the heart rudiment. In silico cloning based on the medaka genome database showed another mMYHs of the slow/cardiac types, mMYH(C3) and mMYH(C4).

Molecular cloning and mRNA expression analysis of carp embryonic, slow and cardiac myosin heavy chain isoforms

Three embryonic class II myosin heavy chains (MYHs) were cloned from the common carp (Cyprinus carpio L.), MYHemb1, MYHemb2 and MYHemb3. MYH DNA clones were also isolated from the slow muscle of adult carp acclimated to 10 degrees C (MYHS10) and 30 degrees C (MYHS30). Phylogenetic analysis demonstrated that MYHemb1 and MYHemb2 belonged to the fast skeletal muscle MYH clade. By contrast, the sequence of MYHemb3 was similar to the adult slow muscle isoforms, MYHS10 and MYHS30. MYHemb1 and MYHemb2 transcripts were first detected by northern blot analysis in embryos 61 h post-fertilization (h.p.f.) at the heartbeat stage, with peak expression occurring in 1-month-old juveniles. MYHemb1 continued to be expressed at low levels in 7-month-old juveniles when MYHemb2 was not detectable. MYHemb3 transcripts appeared at almost the same stage as MYHemb1 transcripts did (61 h.p.f.), and these genes showed a similar pattern of expression. Whole mount in situ hybridization analysis revealed that the transcripts of MYHemb1 and MYHemb2 were expressed in the inner part of myotome, whereas MYHemb3 was expressed in the superficial compartment. MYHS10 and MYHS30 mRNAs were first detected at hatching. In adult stages, the expression of slow muscle MYH mRNAs was dependent on acclimation temperature. MYHS10 mRNA was expressed at an acclimation temperature of 10 and 20 degrees C, but not at 30 degrees C. In contrast, MYHS30 mRNA was strongly expressed at all acclimation temperatures. The predominant MYH transcripts found in adult slow muscle and in embryos at hatching were expressed in adult fast muscle at some acclimation temperatures but not others. A MYH DNA clone was isolated from the cardiac muscle of 10 degrees C-acclimated adult fish (MYHcard). MYHcard mRNA was first detected at 61 h.p.f., but strong signals were only observed in the adult myocardium. The present study has therefore revealed a complex pattern of expression of MYH genes in relation to developmental stage, muscle type and acclimation temperature. None of the skeletal muscle MYHs identified so far was strongly expressed during the late juvenile stage, indicating further developmentally regulated members of the MYH II gene family remain to be discovered.

Functional analysis on the 5′-flanking region of carp fast skeletal myosin heavy chain genes for their expression at different temperatures

Two types of the fast skeletal myosin heavy chain (MYH) genes were cloned from a genomic DNA library of carp (Cyprinus carpio L.) and named MYH10 and MYH30, which showed the sequence similarity to the MYH cDNAs predominantly expressed in carp acclimated to 10 and 30 degrees C, respectively. The 5'-flanking region of about 3 kbp in size each from MYH10 and MYH30 contained various cis-elements to bind to transcriptional regulatory factors such as MyoD family and myocyte enhancer factor 2 (MEF2) family members. To localize functional regions responsible for the MYH gene expression in a temperature-dependent manner, a series of deletion constructs were prepared from the 5'-flanking region, inserted upstream the luciferase gene in a commercially available plasmid, and injected into the dorsal fast muscle of carp acclimated to 10 and 30 degrees C. The sequence of -1004 to -995 bp with the transcriptional activity in MYH30 was identified as an MEF2 binding site. While the activity given by a sequence of -921 to -824 bp in MYH10 contained only a GATA box, that of the activity of the -1 kbp construct from MYH10 was markedly higher in carp reared at 10 degrees C than fish reared at 30 degrees C. On the other hand, no temperature-dependent expressional regulation was observed for MYH30 even with the full-length construct of -3 kbp. The DNA fragment of -921 to -824 bp in MYH10 and MEF2 binding site in MYH30 interacted with nuclear proteins extracted from carp fast skeletal muscle as revealed by electrophoretic mobility shift assay. The signal intensity of a complex formed between the DNA fragment of MYH10 and nuclear extracts from the 10 degrees C-acclimated carp were higher than those with extracts from the 30 degrees C-acclimated fish. Although MEF2-binding site in MYH30 could form complex with nuclear extracts from the 30 degrees C-acclimated carp, the same or stronger signals were detected in complex formed with extracts from the 10 degrees C-acclimated fish.

Diversity of the pufferfish Takifugu rubripes fast skeletal myosin heavy chain genes

Myosin is a highly conserved, ubiquitous actin-based molecular motor that is distributed as diverse as from prokaryotes to mammalian tissues. Among various types in the myosin family proteins, class II, also called sarcomeric, myosin is a classical, conventional molecule that has been extensively studies on its functional and structural properties. It consists of two heavy chains (MYH) of about 200 kDa and four light chains of about 20 kDa. The exon-intron organization was determined for the major subunit of MYH, which contains ATP-hydrolysis and actin-binding sites, from torafugu (tiger pufferfish) Takifugu rubripes fast skeletal muscles. Comprehensive investigation for fast skeletal MYHs based on the fugu (torafugu) genome database and subsequent construction of their physical map revealed that torafugu contains at least 8 putative skeletal MYHs. Furthermore, genomic structural analysis revealed that skeletal MYHs are not clustered in a single locus, but rather spread to at least four loci, with two of them locating at the mammalian syntenic regions. Such arrangement of torafugu MYHs are in a marked contrast to mammalian fast skeletal MYHs that are clustered in a single locus. These data suggest that an ancient segmental duplication or whole-genome duplication occurred in fish lineage as in many other reported torafugu genes.

The complete genomic sequence of the carp fast skeletal myosin heavy chain gene

We have determined the complete DNA nucleotide sequence of the carp Cyprinus carpio fast skeletal myosin heavy chain (MYH) gene. Introns and exons were predicted by comparison with the corresponding carp MYH cDNAs previously reported. The gene encoded the entire mRNA transcript and contained 5958 nucleotides (nt) including 77 nt 5'-untranslated region, 5796 nt coding region for 1931 amino acids, and 85 nt 3'-untranslated region. The coding region was split by 38 introns and the complete gene contained 11,385 nt. This integration of the carp fast skeletal MYH gene was comparable to those of the rat and chicken embryonic MYH genes, which have 41 and 40 exons, respectively. However, the entire gene size of carp MYH was about half those of rat and chicken due to much smaller size of carp introns. We have also demonstrated that this carp MYH gene belonged to so-called intermediate type in a multigene family of carp fast skeletal muscle MYH in comparison of its nucleotide and deduced amino acid sequences to those of carp MYH cDNAs reported previously.

Temperature-dependent expression patterns of grass carp fast skeletal myosin heavy chain genes

Three types of myosin heavy chain cDNA clone named 10 degrees C, intermediate and 30 degrees C types were isolated from fast skeletal muscles of thermally acclimated grass carp Ctenopharyngodon idellus. Three clones encompassing parts of 3'-translated and entire 3'-untranslated regions showed high heterogeneities in their nucleotide sequences in the 3'-untranslated region. The comparison in the deduced amino acid sequence of the 10 degrees C-type clone with those of the intermediate- and 30 degrees C-type clones showed 88% and 89% identities, respectively. By contrast, the deduced amino acid sequence of the intermediate-type clone shared much higher identity of 97% with its 30 degrees C-type counterpart. Northern blot analysis demonstrated that the 10 degrees C- and 30 degrees C-type clones were predominantly expressed in grass carp acclimated to 10 and 30 degrees C, respectively. The intermediate type was expressed both in grass carp acclimated to 20 and 30 degrees C. Furthermore, expression patterns of the three myosin heavy chain genes were altered in accompaniment with seasonal temperature fluctuation. In autumn and winter grass carp expressed the 10 degrees C-type gene almost exclusively, whereas it was completely replaced by the intermediate- and 30 degrees C-type genes in spring and summer. These results suggest that tetraploid grass carp also undergo an adaptation to fluctuating environmental temperatures by selectively expressing fast skeletal myosin heavy chain isoforms as do diploid common carp previously reported.

Loss of filament-forming ability of myosin by non-enzymatic glycosylation and its molecular mechanism

Carp and scallop myosin and their subfragments (S-1 and rod) were reacted with glucose to investigate the effect of non-enzymatic glycosylation on the functionality of myosin. The filament-forming ability of the myosin rod diminished with the progress of non-enzymatic glycosylation and myosin became soluble in 0.1 M NaCl. The inhibition of the self-assembly of myosin molecules occurred chemically as a result of the increase in negative charge repulsion among myosin molecules and, further, physically as a result of the introduction of the glycosyl units into the surface of the rod region.

Seasonal environmental changes modulate the prolactin receptor expression in an eurythermal fish

Eurythermal fish have evolved compensatory responses to the cyclical seasonal changes of the environment. The complex adaptive mechanisms include the transduction of the physical parameters variations into molecular signals. Studies in carp have indicated that prolactin and growth hormone expression is associated with acclimatization, suggesting that the pituitary gland is a relevant physiological node in the generation of the homeostatic rearrangement that occurs in this adaptive process. Here, we report the cloning and characterization of a full-length carp prolactin receptor cDNA, which codes for the long form of the protein resembling that found in mammalian prolactin receptors. We identified up to three receptor transcript isoforms in different tissues of the teleost and assessed cell- and temporal-specific transcription and protein expression in carp undergoing seasonal acclimatization. The distinctive pattern of expression that carp prolactin receptor (cPRLr) depicts upon seasonal acclimatization supports the hypothesis that prolactin and its receptor are clearly involved in the new homeostatic stage that the eurythermal fish needs to survive during the cyclical changes of its habitat.

Temperature-dependent developmental variation in lobster muscle myosin heavy chain isoforms

The temperature- and developmental-regulation of myosin heavy chain (MyHC) expression and primary sequence was investigated in the abdominal musculature of developing Homarus gammarus larvae acclimated to 10, 14 and 19+/-1 degrees C. MyHC loop 1 (ATP binding) and loop 2 (actin binding) regions were sequenced and compared. The deduced amino acid sequence of MyHC loop 1 showed a development-related increase in net charge from +1 to +2 between larval stages 1 and 2, which was not temperature-dependent. In post-settled stage 9 larvae, minor shifts in amino acid sequence occurred at 19 degrees C, and corresponded to a significant up-regulation of fast myosin mRNA expression. However, no temperature-specific loop 1 isoforms were detected. The deduced amino acid sequence of MyHC loop 2 was not affected by temperature, and the net charge remained +4 throughout development. These findings contrast to previous studies using the common carp, in which temperature-specific MyHC isoform genes were expressed in response to disparate thermal regimes. This raises the question as to whether arthropods do not express specific temperature isoforms but instead rely on shifts in fibre type to accommodate alterations in thermal environment.

Temperature and the expression of seven muscle-specific protein genes during embryogenesis in the Atlantic cod Gadus morhua L

Seven cDNA clones coding for different muscle-specific proteins (MSPs) were isolated from the fast muscle tissue of Atlantic cod Gadus morhua L. In situ hybridization using cRNA probes was used to characterize the temporal and spatial patterns of gene expression with respect to somite stage in embryos incubated at 4 degrees C, 7 degrees C and 10 degrees C. MyoD transcripts were first observed in the presomitic mesoderm prior to somite formation, and in the lateral compartment of the forming somites. MyoD expression was not observed in the adaxial cells that give rise to the slow muscle layer, and expression was undetectable by in situ hybridization in the lateral somitic mesoderm after the 35-somite stage, during development of the final approximately 15 somites. RT-PCR analysis, however, confirmed the presence of low levels of the transcript during these later stages. A phylogenetic comparison of the deduced aminoacid sequences of the full-length MyoD cDNA clone and those from other teleosts, and inference from the in situ expression pattern suggested homology with a second paralogue (MyoD2) recently isolated from the gilthead seabream Sparus aurata. Following MyoD expression, alpha-actin was the first structural gene to be switched on at the 16-somite stage, followed by myosin heavy chain, troponin T, troponin I and muscle creatine kinase. The final mRNA in the series to be expressed was troponin C. All genes were switched on prior to myofibril assembly. The troponin C sequence was unusual in that it showed the greatest sequence identity with the rainbow trout Oncorhynchus mykiss cardiac/slow form, but was expressed in the fast myotomal muscle and not in the heart. In addition, the third TnC calcium binding site showed a lower level of sequence conservation than the rest of the sequence. No differences were seen in the timing of appearance or rate of posterior progression (relative to somite stage) of any MSP transcripts between embryos raised at the different temperatures. It was concluded that myofibrillar genes are activated asynchronously in a distinct temporal order prior to myofibrillar assembly and that this process was highly canalized over the temperature range studied.

Stability and emulsion-forming ability of water-soluble fish myofibrillar protein prepared by conjugation with alginate oligosaccharide

Carp myofibrillar protein (Mf) was conjugated with alginate oligosaccharide (AO) through the Maillard reaction under low relative humidity, and the functional properties of the Mf-AO conjugate were investigated under different NaCl concentrations and pH levels. Mf became highly solubilized at lower NaCl concentrations by conjugation with AO, with a slight loss of available lysine. The thermal stability of Mf was effectively improved by conjugation with AO. Heat treatment at 80 degrees C for 2 h had no effect on the solubility of the Mf-AO conjugate attached to 227 microg/mg of AO regardless of the NaCl concentration and pH. Furthermore, the Mf-AO conjugate showed excellent emulsion-forming ability regardless of NaCl concentration. The improved functionalities of Mf by conjugation with AO remained even at a nearly isoelectric point. These results indicate that conjugation with AO through the Maillard reaction is an effective way to prepare high-functional food material from fish muscle protein.

Variable N-terminal regions of muscle myosin heavy chain modulate ATPase rate and actin sliding velocity

We integratively assessed the function of alternative versions of a region near the N terminus of Drosophila muscle myosin heavy chain (encoded by exon 3a or 3b). We exchanged the alternative exon 3 regions between an embryonic isoform and the indirect flight muscle isoform. Each chimeric myosin was expressed in Drosophila indirect flight muscle, in the absence of other myosin isoforms, allowing for purified protein analysis and whole organism locomotory studies. The flight muscle isoform generates higher in vitro actin sliding velocity and solution ATPase rates than the embryonic isoform. Exchanging the embryonic exon 3 region into the flight muscle isoform decreased ATPase rates to embryonic levels but did not affect actin sliding velocity or flight muscle ultrastructure. Interestingly, this swap only slightly impaired flight ability. Exchanging the flight muscle-specific exon 3 region into the embryonic isoform increased actin sliding velocity 3-fold and improved indirect flight muscle ultrastructure integrity but failed to rescue the flightless phenotype of flies expressing embryonic myosin. These results suggest that the two structural versions of the exon 3 domain independently influence the kinetics of at least two steps of the actomyosin cross-bridge cycle.

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.

Temperature plasticity of contractile proteins in fish muscle

Three myosin heavy chain isoforms with different actin-activated Mg2+-ATPase activities were found in the fast skeletal muscle from carp (Cyprinus carpio) acclimated to 10 and 30°C. The composition of three types of myosin heavy chain was dependent on acclimation temperature,demonstrating the presence of temperature-specific myosin isoforms in carp. Subsequently, the temperature-dependence of the sliding velocity of fluorescent F-actin in myosins isolated from 10°C- and 30°C-acclimated carp was measured. At 8°C, the filament velocity was three times higher for myosin from 10°C- than from 30°C-acclimated fish. Activation energies (Ea) for the sliding velocity of F-actin were 63 and 111 kJ mol-1 for myosins from 10°C- and 30°C-acclimated fish, respectively. Activation energy for actin-activated Mg2+-ATPase activity was 0.46 kJ mol-1 in myosin from 10°C-acclimated fish and 0.54 kJ mol-1 in myosin from 30°C-acclimated fish. The inactivation rate constant(KD) of Ca2+-ATPase was 7.5×10-4s-1 at 30°C for myosin from 10°C-acclimated fish, which was approximately twice that for myosin from 30°C-acclimated fish. It is suggested that these differences in thermostability reflect a more flexible structure of the myosin molecule in cold-acclimated carp, which results in a reduced activation enthalpy for contraction and, hence, a higher sliding velocity at low temperatures. Structural analysis of cDNAs encoding the carp myosin heavy chain demonstrated striking differences in two surface loops of myosin subfragment-1 (S1), loops 1 and 2, between the 10°C and 30°C types, which were predominantly expressed in carp acclimated to 10°C and 30°C, respectively. Chimeric myosins composed of Dictyostelium discoideum myosin backbones with loop sequences of carp S1 heavy chain isoforms demonstrated that the diversity of the loop 2 sequence of carp S1 affected the Vmax of actin-activated Mg2+-ATPase activity.

Comparison of the variable loop regions of myosin heavy chain genes from Antarctic and temperate isopods

The evolutionary adaptations of functional genes to life at low temperatures are not well characterised in marine and fresh water invertebrates. Temperature has been shown to affect the functional characteristics of fish muscles, with changes in the velocity of shortening and ATPase activity being associated with myosin heavy chain (MyHC) isoform composition and the structure of the surface loop regions. Two PCR products spanning loops 1 and 2 of a MyHC gene from an Antarctic isopod (Glyptonotus antarcticus) were sequenced and compared with those of a temperate isopod (Idotea resecata), slow and fast fibres from lobster (Homarus gammarus) and a cold water amphipod (Eulimnogammarus verrucosus), revealing specific differences between the species, possibly related to fibre type and habitat temperature. The loop 2 region from G. antarcticus myosin was cloned and used for Northern analysis of total RNA from the other species. The cloned myosin cDNA hybridised specifically to a 6.6-kb transcript, in G. antarcticus muscle. In contrast, cDNA probes for lobster slow myosin and actin hybridised to muscle RNA from all species, demonstrating that a distinct MyHC isoform is expressed in the Antarctic isopod, as opposed to the temperate species. The inter- and intra-specific sequence differences in loop 2 region suggest that this may be a site for muscle adaptation to enable function at the low temperatures found in the Southern Ocean.

Embryonic temperature and the relative timing of muscle-specific genes during development in herring (Clupea harengus L.)

Temperature influences many aspects of muscle development in herring (Clupea harengus). In Clyde herring, myofibril synthesis occurred later with respect to somite stage in embryos reared at 5°C compared with 12°C. The aim of the present study was to test the hypothesis that the relative timing of expression of myogenic regulatory factors (MRFs) and myosin heavy chain (MyHC) transcripts changes with developmental temperature. Reverse transcriptase/polymerase chain reaction (RT-PCR) was used to clone partial coding regions of MyoD, myogenin and MyHC from juvenile Clyde herring. Embryos were reared at 5, 8 and 12°C, and the spatial and temporal expression patterns of transcripts were investigated using cRNA probes and in situ hybridisation. Antisense probes revealed a rostral–caudal progression of all three transcripts. MyoD transcription initially took place in the adaxial cells of the unsegmented, presomitic mesoderm, whereas myogenin transcription first occurred in newly formed somites. The MyHC gene transcript was not detected until approximately nine somites had formed. Since the somite stage at which the MRFs and MyHC were first expressed was independent of temperature, the hypothesis was rejected. We suggest that the effects of temperature on myofibril synthesis must occur downstream from MyHC transcription either at the level of translation or at the assembly stage.

Characterisation of red and white muscle myosin heavy chain gene coding sequences from antarctic and tropical fish

To understand molecular adaptation for locomotion at different environmental temperatures, we have studied the myosin heavy chain genes as these encode the molecular motors involved. For this purpose, cDNA libraries from white (fast) and red (slow) myotomal muscle of an Antarctic and a tropical fish were constructed and from these different myosin heavy chain cDNAs were isolated. Northern and in situ hybridisation confirmed in which type of muscle these isoform genes are expressed. The cDNAs were sequenced and the structure of the ATPase sites compared. There was a marked similarity between the tropical fast myosin and the Antarctic slow myosin in the loop 1 region, which has similar amino acid side chains, charge distribution and conformation. These findings help to explain why the myofibrils isolated from white muscle of tropical fish show a lower specific ATPase activity than the white muscle of Antarctic fish but a similar activity to the Antarctic red (slow) muscle. It also provides insight into the way molecular motors in Antarctic fish have evolved to produce more power and thus ensure effective swimming at near zero temperatures by the substitution or addition of a few residues in strategic regions, which include the ATPase site.

Environmental acclimatization of the carp modulates the transcription of beta-actin

A cascade of mechanisms involving changes in gene expression are substantial to shape the adaptive responses that a eurythermal fish requires upon environmental changes in its habitat. We have previously shown that the cyclical reprogramming of rRNA transcription is a remarkable feature in carp under seasonal acclimatization. Using in situ hybridization and competitive RT-PCR we found significant differences in beta-actin transcripts, generally accepted to be coded by a typical housekeeping gene, in tissues from summer- and winter-acclimatized carp. The physiological differential beta-actin transcription herein reported places us on the alert for the reference genes estimated to be constitutive to quantitatively assess gene transcripts.

Structure-function relationships of the two surface loops of myosin heavy chain isoforms from thermally acclimated carp

The structure-function relationships of fast skeletal myosin isoforms remain poorly understood. To shed some light, we constructed chimeric myosins comprised of Dictyostelium myosin heavy chain backbone with carp loop sequences and analyzed their functional properties. A loop 2-10 chimeric myosin having the loop 2 sequence of the fast skeletal isoform predominantly expressed in carp acclimated to 10 degrees C showed V(max) in actin-activated Mg(2+)-ATPase activity 1.4-fold higher than a loop 2-30 chimera constructed from the loop 2 sequence of the dominant isoform in carp acclimated to 30 degrees C. These two chimera exhibited no significant differences in sliding velocity of actin filaments in in vitro motility assay. Contrastingly, both loop 1-associated chimeras, loop 1-10 and loop 1-30, did not differ in both ATPase activity and in sliding velocity of actin filaments.

Variable surface loops and myosin activity: accessories to a motor

The catalytic head of myosin is a globular structure that has historically been divided into three segments of 25, 50, and 20 kDa. The solvent-exposed, proteolytically-sensitive surface loops of myosin that join these three segments are highly variable in their sequences. While surface loops have not traditionally been thought to affect enzymatic activities, these loops lie near the ATP and actin-binding sites and have been implicated in the modulation of myosin's kinetic activities. In this work we review the wealth of data regarding the loops that has accumulated over the years and discuss the roles of the loops in contributing to the different activities displayed by different myosin isoforms.

Raman spectroscopic study of changes in fish actomyosin during setting

Actomyosins (AMs) isolated from tilapia, lemon sole, ling cod, and rock fish were heated at 40 degrees C, and structural changes in AMs were investigated using Raman spectroscopy to elucidate low-temperature gelling phenomenon, that is, "setting", of surimi. The following conformational transitions were observed in lemon sole, ling cod, and rock fish gels during setting: a slow unfolding of alpha-helix and exposure of hydrophobic amino acid residues occurring in long-time incubation at 40 degrees C, thereby forming hydrophobic interactions among AM molecules. In addition, the most frequent conformation in disulfide bonds was gauche-gauche-trans (g-g-t) form in the set gel. On the other hand, tilapia AM did not form a gel with heating at 40 degrees C, its alpha-helical structure in the myosin being far more stable than that of the other species. The heat resistance of the tight alpha-helix may prevent the gelation of tilapia AM. It is, therefore, likely that the unfolding of the alpha-helix of myosin is a prerequisite for gelation of AM during setting.

Specialized conservation of surface loops of myosin: evidence that loops are involved in determining functional characteristics

The molecular motor myosin has been the focus of considerable structure-function analysis. Of key interest are the portions of the protein that control the rate of ATP hydrolysis, the affinity for actin, and the velocity at which myosin moves actin. Two regions that have been implicated in determining these parameters are the "loop" regions at the junctions of the 25 kDa and 50 kDa domains and the 50 kDa and 20 kDa domains of the protein. However, the sequences of these regions are poorly conserved between different myosin families, suggesting that they are not constrained evolutionarily, and thus are relatively unimportant for myosin function. In order to address this apparent incongruity, we have performed an analysis of relative rates of observed evolutionary change. We found that the sequences of these loop regions appear to be actually more constrained than the sequences of the rest of the myosin molecule, when myosins are compared that are known to be kinetically or developmentally similar. This suggests that these loop regions could play an important role in myosin function and supports the idea that they are involved in modulating the specific kinetic characteristics that functionally differentiate one myosin isoform from another. Apparently "unconserved" loops may generally play a role in determining kinetic properties of enzymes, and similar analyses of relative rates of evolution may prove useful for the study of structure-function relationships in other protein families.

Characterization of the carp myosin heavy chain multigene family

We isolated partial coding sequences for 29 carp myosin heavy chain genes (MyoHCs) and determined the nucleotide sequences around the region encoding the loop 2 of the myosin molecule. The predicted amino acid sequences from the isolated genes all showed very high similarity to those of skeletal and cardiac muscles from higher vertebrates, but not to those of smooth and non-muscle counterparts. Among all clones isolated, carp MyoHC10, MyoHCI-1-3 and MyoHC30 showed exon-nucleotide sequences identical to those of cDNAs encoding the loop 2 region of the 10 degrees C-, intermediate- and 30 degrees C-type fast skeletal isoforms [Hirayama and Watabe, Euro. J. Biochem. 246 (1997) 380-387]. The loop 2 of 28 types of carp MyoHCs was encoded by two exons separated by an intron corresponding to that of the 16th in higher vertebrate MyoHCs, whilst this intron was not found in carp MyoHC30. Although carp MyoHC30 had a gene organization different from those of higher vertebrates and other carp MyoHCs, its predicted amino acid sequence for loop 2 showed the highest homology to those of higher vertebrates among carp MyoHCs. In the 28 carp MyoHCs containing the intron, a combination of different nucleotide sequences for the two resulted in 14 distinct series for the combined coding sequence. These different nucleotide sequences encoded nine distinct amino acid sequences. Phylogenetic analysis for the present loop 2 and light meromyosin previously reported for carp MyoHCs [Imai et al., J. Exp. Biol. 200 (1997) 27-34] revealed that carp MyoHCs have recently diverged and are more closely related to each other than to MyoHCs from other species.