Study on the myosin like protein from brwn alga Laminaria japonica

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A cDNA encoding myosin-like protein(LjMLP)was cloned from brown alga Laminaria japonica. LjMLP consists of 634 amino acids, which showed the significant homology with sequences of other species myosin motor domain, but there is no region corresponding to loop-2, converter, neck, and tail domains of other myosins in LjMLP. Recombinant LjMLP(rLjMLP)was expressed in insect cells and purified in the absence or presence of L. japonica calmodulin (LjCaM). When rLjMLP was co-expressed with rLjCaM, purified rLjMLP showed that actin-activated Mg-ATPase and actin translocation activities. rLjCaM showed the highest Mg-ATPase activity(0.68 1/sec)at 25℃ in the presence of 40μM F-actin. Actin movement was observed with the velocity of 0.03μm/sec at 25℃ in in vitro motility assay. Genomic DNA analysis revealed LjMLP gene was comprised of four exons interleaved with three introns. According to RT-PCR analysis, mRNA of LjMLP was expressed independent of cultivated-season of L. japonica.