Large Isoforms of UNC-89 (Obscurin) Are Required for Muscle Cell Architecture and Optimal Calcium Release in Caenorhabditis elegans

Calcium, a ubiquitous intracellular signaling molecule, controls a diverse array of cellular processes. Consequently, cells have developed strategies to modulate the shape of calcium signals in space and time. The force generating machinery in muscle is regulated by the influx and efflux of calcium ions into the muscle cytoplasm. In order for efficient and effective muscle contraction to occur, calcium needs to be rapidly, accurately and reliably regulated. The mechanisms underlying this highly regulated process are not fully understood. Here, we show that the Caenorhabditis elegans homolog of the giant muscle protein obscurin, UNC-89, is required for normal muscle cell architecture. The large immunoglobulin domain-rich isoforms of UNC-89 are critical for sarcomere and sarcoplasmic reticulum organization. Furthermore, we have found evidence that this structural organization is crucial for excitation-contraction coupling in the body wall muscle, through the coordination of calcium signaling. Thus, our data implicates UNC-89 in maintaining muscle cell architecture and that this precise organization is essential for optimal calcium mobilization and efficient and effective muscle contraction

Three redox states of metallonitrosyls in aqueous solution

This contribution deals with the structure and reactivity of bound nitrosyl in transition-metal centers (group 8: Fe, Ru, Os). The focus is set on pseudooctahedral nitrosyl-complexes with coordination number 5 and 6, containing ancillary coligands of both heme- and nonheme type. The discussion is organized in terms of Enemark and Feltham's classification, selecting complexes within the {MNO}n framework (n=6, 7, and 8). The examples have been chosen for a best description of the electronic structures in terms of modern structural, spectroscopical, and computational methodologies. The selected {MNO}6,7,8 species reflect the occurrence of three redox states of bound nitrosyl, frequently (though not always) described as NO+, NO, and NO- for n=6, 7, and 8, respectively. The analysis is centered on the members of a series of complexes for which the three redox states have been observed on the same platform, viz., [Fe(CN)5(NO)]2,3,4- and [Ru(Me3[9]aneN3)(bpy)(NO)]3,2,1+, in aqueous solutions. The influence of the donor-acceptor character of the coligands is specifically addressed with emphasis on the ligand trans- to nitrosyl, showing that the latter group may exert a delabilizing influence (as NO+), as well as a labilizing one (NO-≫NO) on the trans-ligand. On the other hand, typical electrophilic reactivity patterns (toward different nucleophiles) are analyzed for M-NO+, and nucleophilic reactivity (with O2) is described for the reduced species, M-NO and M-(NO-). In the latter case, protonation is described by characterizing the bound HNO species. Important differences are highlighted in the chemistry of bound NO- and HNO, revealing the strong and mild reductant abilities of these species, respectively. The chemistry is analyzed in terms of the biological relevance to the behavior of nitrite- and NO-reductases and other NO-related enzymes.Fil: Bari, Sara Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Olabe Iparraguirre, Jose Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Slep, Leonardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentin