References of "Bunster, Marta"
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See detailIn silico model of an antenna of a phycobilisome and energy transfer rates determination by theoretical Forster approach.
Figueroa, Maximiliano ULg; Martinez-Oyanedel, Jose; Matamala, Adelio R. et al

in Protein Science : A Publication of the Protein Society (2012)

Energy transfer (ET) in phycobilisomes, a macrocomplex of phycobiliproteins and linker proteins, is a process that is difficult to understand completely. A model for a rod composed of two hexamers of ... [more ▼]

Energy transfer (ET) in phycobilisomes, a macrocomplex of phycobiliproteins and linker proteins, is a process that is difficult to understand completely. A model for a rod composed of two hexamers of Phycocyanin and two hexamers of Phycoerythrin was built using an in silico approach and the three-dimensional structures of both phycobiliproteins from Gracilaria chilensis. The model was characterized and showed 125 A wide and 230 A high, which agree with the dimensions of a piling of four hexamers as observed in the images of subcomplexes of phycobilisomes obtained by transmission electron microscopy. ET rates between every pair of chromophores in the model were calculated using the Forster approach, and the fastest rates were selected to draw preferential ET pathways along the rod. Every path indicates that the ET is funneled toward the chromophores located at Cysteines 82 in Phycoerythrin and 84 in Phycocyanin. The chromophores that face the exterior of the rod are phycoerythrobilins, and they also show a preferential ET toward the chromophores located at the center of the rod. The values calculated, in general, agree with the experimental data reported previously, which validates the use of this experimental approach. [less ▲]

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See detailBiophysical studies support a predicted superhelical structure with armadillo repeats for Ric-8.
Figueroa, Maximiliano ULg; Hinrichs, Maria Victoria; Bunster, Marta et al

in Protein Science : A Publication of the Protein Society (2009), 18(6), 1139-45

Ric-8 is a highly conserved cytosolic protein (MW 63 KDa) initially identified in C. elegans as an essential factor in neurotransmitter release and asymmetric cell division. Two different isoforms have ... [more ▼]

Ric-8 is a highly conserved cytosolic protein (MW 63 KDa) initially identified in C. elegans as an essential factor in neurotransmitter release and asymmetric cell division. Two different isoforms have been described in mammals, Ric-8A and Ric-8B; each possess guanine nucleotide exchange activity (GEF) on heterotrimeric G-proteins, but with different Galpha subunits specificities. To gain insight on the mechanisms involved in Ric-8 cellular functions it is essential to obtain some information about its structure. Therefore, the aim of this work was to create a structural model for Ric-8. In this case, it was not possible to construct a model based on comparison with a template structure because Ric-8 does not present sequence similarity with any other protein. Consequently, different bioinformatics approaches that include protein folding and structure prediction were used. The Ric-8 structural model is composed of 10 armadillo folding motifs, organized in a right-twisted alpha-alpha super helix. In order to validate the structural model, a His-tag fusion construct of Ric-8 was expressed in E. coli, purified by affinity and anion exchange chromatography and subjected to circular dichroism analysis (CD) and thermostability studies. Ric-8 is approximately 80% alpha helix, with a Tm of 43.1 degrees C, consistent with an armadillo-type structure such as alpha-importin, a protein composed of 10 armadillo repeats. The proposed structural model for Ric-8 is intriguing because armadillo proteins are known to interact with multiple partners and participate in diverse cellular functions. These results open the possibility of finding new protein partners for Ric-8 with new cellular functions. [less ▲]

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See detailThe structure at 2 A resolution of Phycocyanin from Gracilaria chilensis and the energy transfer network in a PC-PC complex.
Contreras-Martel, Carlos; Matamala, Adelio; Bruna, Carola et al

in Biophysical Chemistry (2007), 125(2-3), 388-96

Phycocyanin is a phycobiliprotein involved in light harvesting and conduction of light to the reaction centers in cyanobacteria and red algae. The structure of C-phycocyanin from Gracilaria chilensis was ... [more ▼]

Phycocyanin is a phycobiliprotein involved in light harvesting and conduction of light to the reaction centers in cyanobacteria and red algae. The structure of C-phycocyanin from Gracilaria chilensis was solved by X-ray crystallography at 2.0 A resolution in space group P2(1). An interaction model between two PC heterohexamers was built, followed by molecular dynamic refinement. The best model showed an inter-hexamer rotation of 23 degrees . The coordinates of a PC heterohexamer (alphabeta)(6) and of the PC-PC complex were used to perform energy transfer calculations between chromophores pairs using the fluorescence resonance energy transfer approach (FRET). Two main intra PC ((I)beta(3)(82)-->(I)alpha(1)(84)-->(I)alpha(5)(84)-->(I)beta(6)(82) and (I)beta(3)(153)-->(I)beta(5)(153)) and two main inter PC ((I)beta(6)(82)-->(II)beta(3)(82) and (I)beta(5)(153)-->(II)beta(3)(153)) pathways were proposed based on the values of the energy transfer constants calculated for all the chromophore pairs in the hexamer and in the complex. [less ▲]

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