Smooth and striated muscle a-tropomyosins differ as a consequence of alternative splicing of exons 2 and 9 encoding amino acid residues 39-80 and 258-284, respectively [Ruiz-Opazo, N., Weinberger, J. & Nadal-Ginard, B. (1985) Nature (London) 315, 67-70]. To understand the relationship between alternatively spliced exons and functional domains in tropomyosin, recombinant unacetylated striated muscle, smooth muscle, and chimeric rat a-tropomyosins (+H3N-tropomyosins) expressed in and purified from Escherichia coli were analyzed. The functional differences between the isoforms can be primarily ascribed to exon 9. 'H3N-Tropomyosins with the smooth muscle exon 9 bound to skeletal muscle filamentous actin with at least a 5-fold higher affinity than 'H3N-tropomyosins with the striated muscle exon 9. On the other hand, in the presence of Ca2+, troponin increased the affinity of 'H3N-tropomyosins with the striated muscle exon 9 at least 50-fold, whereas it had little effect on 'H3N-tropomyosins with the smooth muscle exon 9. The unique striated muscle ae-tropomyosin exon 9 seems to be specialized for Ca2 -insensitive interaction with troponin on the thin filament. The unique smooth muscle a-tropomyosin exon 2 was associated with a slightly lower actin affinity than the striated muscle exon 2. Although the regions encoded by exons 2 and 9 correspond to functional domains, they are not recognizable as independent units or structural domains in the extended coiled-coil structure of this fibrous actin binding protein.

No abstract

The effect of bathymetry near the south sea area of Korea on the propagation of 2011 East Japan Tsunami is analyzed based on the numerical simulation using the finite difference dispersion-correction model. It is found that the bathymetry from the source to Korean Peninsula, such as Nankai Trough, Ryukyu Islands and the topographical lens in the East China Sea, plays an important role to reduce the tsunami height along the south coast of Korea. The mechanism involved in the transformation of tsunamis over those topographies is discussed.

No abstract

No abstract