Probing the calcium-induce conformational transition of troponin C with site-directed mutants

Article Abstract:

Contraction of cardiac and skeletal muscle is regulated by binding calcium to troponin, which contains three subunits with distinct activities: troponin C, troponin I, and troponin T. The troponin C molecule has been isolated, purified and examined by X-ray crystallography so that its three-dimensional structure is known. The calcium molecule induces changes in the shape of the troponin C molecule. Using site-directed mutagenesis (in which a particular area of the DNA that encodes the gene is altered), the sites and the mechanism of muscle contraction regulation can be studied. The regulatory sites have been identified to be sites which bind calcium at one end of the troponin molecule. The molecule was bridged together using site-directed mutagenesis, which inhibited the mobility of the molecule and the binding of calcium. The altered troponin molecule was introduced into muscle fibers and muscle contraction was no longer regulated, indicating that these changes affected other molecules involved in muscle contraction. These studies will lead to the further understanding of how muscle contraction occurs and how it is regulated. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Muscle regulation: on the other hand

Article Abstract:

The contraction of cardiac and skeletal muscles is regulated by two proteins, troponin and tropomyosin, which interact with actin filaments (molecules that are involved in the contraction and relaxation of muscle). Troponin contains three subunits, which have distinct activities. Using site-directed mutagenesis (in which a particular area of the DNA that encodes the gene is altered) the sites and mechanisms that regulate muscle contraction can be studied. One of the troponin subunits has been isolated and purified so that the structure of the molecule can be studied by X-ray crystallography. The regulatory sites have been identified as sites that bind the mineral calcium at one end of the troponin molecule. Therefore, regulation of muscle contraction by troponin is dependent on calcium binding to the molecule at these sites; this causes a change in the shape of the molecule, and affects the ability of the one of the subunits of the troponin molecule to interact with another subunit and regulate muscle contraction. These studies will lead to greater understanding of how muscle contraction occurs and how it is regulated. (Consumer Summary produced by Reliance Medical Information, Inc.)

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The genome sequence of the plant pathogen Xylella fastidiosa

Article Abstract:

The complete genome sequence of a plant pathogen affecting citrus plants, Xylella fastidiosa, is presented. The structure of the genome is described and the carbon and energy sources of the bacterium are discussed.

Analysis, Cover Story, Fruit industry, Fruit trade, Genomes, Genetic research, Maps (Geography)

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