Modified helix-loop-helix motifs of calmodulin: the influence of the exchange of helical regions on calcium-binding affinity

The four calcium-binding sites, called the helix-loop-helix, or the EF-hand motifs, of calmodulin differ in their ion-binding affinities; this has been thought to arise due to the variations in the sequences of the loop regions where the ion binds. We focus attention here on the role of the flanking helical regions on the calcium-binding affinities. Peptides were synthesized in a manner that simulates the E and F helical flanks of site 4 (the strongest calcium-binding site of the calmodulin) to sandwich the loop sequences of sites 1, 2, 3 and 4 so as to produce peptides named 414, 424, 434 and 444, as well as using the helical flanks of site 1 (the weakest site) to produce peptides 111, 121, 131 and 141. Calcium binding was monitored using the calcium-mimic dye Stains-all (4,4,4',5'-dibenzo-3,3'-diethyl-9-methyl-thiacarbocya-nine bromide). Binding abilities were seen to increase several-fold when the E and F helices of site 1 were replaced by those of site 4 (i.e., 111-414). In contrast, the intensity of circular dichroism induced in the absorption bands of the bound achiral dye decreased significantly when the helical flanks of site 4 were replaced with those of site 1 (i.e., 444-141). The helical flanks of site 4 impart greater binding ability to a given loop region, while the helical flanks of site 1 tend to weaken it

Visualización en tres dimensiones, los mapas de amenaza volcánica educan al ciudadano común

Even the most reliable volcanic hazard map will be of little use, unless it is presented in terms that are useful to politics, emergency management officials and citizens. The Volcanic Hazard Map of the Nevado del Ruiz Volcano (Colombia), was superimposed on Landsat TM 5 data and digital elevation models, in order to generate perspective views for making the volcanic hazard situations comprehensible to the common people.This 3-D visualization methodology could be used with any volcanic hazard map available. The products generated help to improve the communication between volcanologists and people not familiar with volcanoes, in order to avoid confusion, misunderstanding and strained relations between scientists and persons responsible for the public welfare, during any volcanic emergency crisis.Hasta el mapa de amenaza volcánica más confiable, será de poca utilidad si es presentado de una forma que no lo haga útil para políticos, oficiales que manejan situaciones de emergencia y ciudadanos comunes. Se realizó la superposición del Mapa de Amenaza Volcánica del Volcán Nevado del Ruiz (Colombia), sobre imágenes Landsat TM y modelos digitales de elevación, para generar vistas en perspectiva que hagan comprensibles para el público en general, las situaciones de amenaza volcánica.Esta metodología de visualización en tres dimensiones, podría utilizarse en cualquier mapa de amenaza volcánica disponible. Los productos generados ayudan a mejorar la comunicación entre vulcanólogos y gente no familiarizada con los volcanes, para evitar confusiones, malos entendidos y malas relaciones entre científicos y personas a cargo de la seguridad pública, durante cualquier crisis de emergencia volcánica. &nbsp

Calcium and chlorpromazine binding to the EF-hand peptides of neuronal calcium sensor-1

Neuronal calcium sensor-1, a protein of calcium sensor family, is known to have four structural EF-hands. We have synthesised peptides corresponding to all the four EF-hands and studied their conformation and calcium-binding. Our data confirm that the first putative site, a non-canonical one (EF1), does not bind calcium. We have investigated if this lack of binding is due to the presence of non-favoured residues (particularly at +x and -z co-ordinating positions) of the loop. We have mutated these residues and found that after modification the peptides bound calcium. However, these mutated peptides (EF1 and its functional mutants) do not show any Ca<SUP>2+</SUP> induced changes in far-UV CD. EF2, EF3, and EF4 peptides bind Ca<SUP>2+</SUP>, EF3 being the strongest binder, followed by EF4. Our data of Ca<SUP>2+</SUP>-binding to individual EF peptides show that there are three active Ca<SUP>2+</SUP>-binding sites in NCS-1. We have also studied the binding of a neuroleptic drug, chlorpromazine, with the protein as well as with its EF-hands. CPZ binds myristoylated as well as non-myristoylated NCS-1 in Ca<SUP>2+</SUP>-dependent manner, with dynamic interaction to myristoylated protein. CPZ does not bind to EF1, but binds to functional EF-hand peptides and induces changes in far-UV CD. Our results suggest that NCS-1 could be a target of such antipsychotic and neuroleptic drugs