Planarian myosin essential light chain is involved in the formation of brain lateral branches during regeneration.

The myosin essential light chain (ELC) is a structure component of the actomyosin cross-bridge, however, the functions in the central nervous system (CNS) development and regeneration remain poorly understood. Planarian Dugesia japonica has revealed fundamental mechanisms and unique aspects of neuroscience and neuroregeneration. In this study, the cDNA DjElc, encoding a planarian essential light chain of myosin, was identified from the planarian Dugesia japonica cDNA library. It encodes a deduced protein with highly conserved functionally domains EF-Hand and Ca(2+) binding sites that shares significant similarity with other members of ELC. Whole mount in situ hybridization studies show that DjElc expressed in CNS during embryonic development and regeneration of adult planarians. Loss of function of DjElc by RNA interference during planarian regeneration inhibits brain lateral branches regeneration completely. In conclusion, these results demonstrated that DjElc is required for maintenance of neurons and neurite outgrowth, particularly for involving the brain later branch regeneration.

Gene duplication and conversion events shaped three homologous, differentially expressed myosin regulatory light chain (MLC2) genes.

Myosin II is a hexameric protein complex consisting of two myosin heavy chains, two myosin essential light chains and two myosin regulatory light chains. Multiple subunit isoforms exist, allowing great diversity in myosin II composition which likely impacts on its contractile properties. Little is known about the evolutionary origin, expression pattern and function of myosin regulatory light chain (MLC2) isoforms. We analysed the evolutionary relationship between smooth muscle (sm), nonmuscle (nm) and nonmuscle-like (nml) MLC2 genes, which encode three homologous proteins expressed in nonmuscle cells. The three genes arose by successive gene duplication events. The high sequence similarity between the tandemly arranged nm- and nml-MLC2 genes is best explained by gene conversion. Urea/glycerol-polyacrylamide gel electrophoresis and RNA analysis were employed to monitor expression of sm-, nm- and nml-MLC2 in human and mouse cell lines. Conspicuous differences between transformed and non-transformed cells were observed, with sm-MLC2 being suppressed in Ras-transformed cells. Our findings shed light on the evolutionary history of three homologous MLC2 proteins and point to isoform-specific cell growth-related roles in nonmuscle cell myosin II contractility.

A proteomic-based approach for detection of chicken in meat mixes.

A proteomic-based method has been developed for the detection of chicken meat within mixed meat preparations. The procedure is robust and simple, comprising the extraction of myofibrillar proteins, enrichment of target proteins using OFFGEL isoelectric focusing, in-solution trypsin digestion of myosin light chain 3, and analysis of the generated peptides by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Using this approach, it was possible for example to detect 0.5% contaminating chicken in pork meat with high confidence. Quantitative detection of chicken meat was done by using AQUA stable isotope peptides made from the sequence of previously selected species-specific peptide biomarkers. Linearity was observed between the amount of the peptide biomarker and the amount of chicken present in the mixture; further independent replication is required now to validate the method. Apart from its simplicity, this approach has the advantage that it can be used effectively for the detection of both raw and cooked meat. The method is robust, reliable, and sensitive, representing a serious alternative to methods currently in use for these purposes. It is amenable to highly processed foods which can be particularly problematic, as the tertiary protein structure is often affected in processed food precluding immunoassays. In addition, this proteomic analysis will permit the determination of definitive discriminatory sequence, unlike the DNA PCR based methods used presently. The present article also demonstrates the translation of the technology to routine mass spectrometry equipment, making the methodology suitable for public analysts.

Expression of cardiac myosin light chain 2 during embryonic heart development in medaka fish, Oryzias latipes, and phylogenetic relationship with other myosin light chains.

Cardiac myosin light chain 2 (MLC-2) plays a key role in heart development, contraction, and embryo and adult heart maintenance. In some animals, defects in the function of cardiac MLC-2 cause hypertrophic cardiomyopathy. To illuminate the functions of cardiac MLC-2 in embryonic heart formation and contraction, and into the evolution of MLC-2, we characterized the expression and requirement for medaka cardiac MLC-2 gene in the developing heart. Medaka cardiac MLC-2 cDNA (mcmlc2) was isolated and its gene expression pattern was determined. The mcmlc2 was found to be expressed in the bilateral cardiac mesoderm, the formed heart tube, and in both the differentiated ventricle and atrium. Knockdown of mcmlc2 function caused severe cardiac disorders, including edema in the atrium and sinus venosus. Using phylogenetic analysis, we found that physiological variations in the MLC-2 molecules evolved due to amino acid changes in the Ca(2+) binding domain during molecular evolution. Our findings concerning the function and expression of mcmlc2 are nearly identical with those of other MLC-2 genes, and our phylogenetic analysis suggests that during evolution, the variations in physiological function within the MLC-2 gene family have arisen from a change in the amino acids in the Ca(2+) binding domain in the MLC-2 molecule.

[Comparative structural analysis of myosin light chains and gene duplication in fish].

Origin and structure of myosin light chain (MLC) proteins have been studied by comparative analysis of fish mlc1, mlc2, and mlc3 genes encoding MLC1, MLC2, and MLC3, respectively. The exon-intron structure of these genes has been analyzed in zebrafish Danio rerio, loach Misgurnus fossilis, fugu Takifugu rubripes, and Nile puffer Tetraodon fahaka. We propose that mlc1 and mlc3 are homologues genes originated by fish-specific whole genome duplication (paralogs). This is supported by high sequence similarity between mlc1 and mlc3 as well as by the exon-intron structure of these genes and their localization on different chromosomes. Exons 2 to 5 of mlc1 and mlc3 are highly conserved and have similar splicing sites. A paralog gene of mlc2 resulting from a similar duplication event has been identified in zebrafish genome. Expression of mlc2 paralog is limited to the larval stages of Danio rerio and to regenerating tissues of the adult fish. There is a possibility that the paralog of mlc2 encodes larval myosin light chain protein (larval MLC) previously reported in a number of fish species.

Identification and characterization of an 8-kDa light chain associated with Dictyostelium discoideum MyoB, a class I myosin.

Dictyostelium discoideum MyoB is a single-headed class I myosin. Analysis of purified MyoB by SDS-PAGE indicated the presence of an approximately 9-kDa light chain. A tryptic digest of MyoB yielded a partial sequence for the light chain that exactly matched a sequence in a 73-amino acid, 8,296-Da protein (dictyBase number DDB0188713). This protein, termed MlcB, contains two EF-hand motifs and shares approximately 30% sequence identity with the N- and C-terminal lobes of calmodulin. FLAG-MlcB expressed in Dictyostelium co-immunoprecipitated with MyoB but not with the related class myosins and MyoD. Recombinant MlcB bound Ca2+ with a Kd value of 0.2 microm and underwent a Ca2+-induced change in conformation that increased alpha-helical content and surface hydrophobicity. Mutational analysis showed that the first EF-hand was responsible for Ca2+ binding. In the presence and absence of Ca2+ MlcB was a monomer in solution and bound to a MyoB IQ motif peptide with a Kd value of approximately 0.5 microm. A MyoB head-neck construct with a Ser to Glu mutation at the TEDS site bound MlcB and displayed an actin-activated Mg2+ ATPase activity that was insensitive to Ca2+. We conclude that MlcB represents a novel type of small myosin light chain that binds to IQ motifs in a manner comparable with a single lobe of a typical four-EF-hand protein.

[Ontogenetic and phylogenetic analysis of myosin light chain proteins from skeletal muscles of loach Misgurnus fossilis].

mRNAs of all three types of myosin light chain proteins are expressed in skeletal muscles of both larval and adult stages of loach Misgurnus fossilis (Cobitidae) and these proteins are encoded by different genes (mlc1, mlc2, and mlc3). No difference was revealed between transcripts from larval stage and adult fish for all three mlc proteins. Our approach (RT-PCR with fish-specific mlc1, mlc2, and mlc3 primers) failed to reveal the larval form of myosin light chain protein found previously by protein electrophoresis of loach fry muscle extract. Comparative analysis of the protein structure shows high homology of MLC1 and MLC3 proteins sharing a large EF-hand calcium-binding domain. Phylogenetic analysis of MLC1 from skeletal muscles of fish and other vertebrate species is concordant with the traditional phylogeny of the group. Within the Teleostei, loach MLC1 had the highest homology with other Cyprinidae, and least with Salmonidae fishes.

Fiber-type-specific expression of essential (alkali) myosin light chains in human skeletal muscles.

We studied the expression patterns of the essential (alkali) myosin light-chain isoforms in adult human skeletal muscles, using in situ hybridization and single-fiber protein analysis. In analogy to other species, we found that the fiber type-specific expression of essential myosin light chains is regulated via the availability of the respective mRNAs in a given fiber. In contrast to other species, the slow isoform 1sa was only expressed in the most oxidative Type I fibers (Subtype IA) in addition to 1sb. These fibers also contained high levels of carbonic anhydrase III. Within the fibers, the essential myosin light-chain mRNAs were located preferentially in the perinuclear regions and to a lesser extent in the intermyofibrillar spaces, a distribution that excludes cotranslational assembly of these light chains into the myofibrils as the main mechanism. In comparing leg and shoulder muscles, we found less distinct fiber typing in the expression patterns of the essential myosin light chains in the leg muscles than in muscles from the shoulder region.