Cristalização e Análises Cristalográficas da Triose Fosfato Isomerase de Naegleria gruberi Resumo: A enzima Triose fosfato isomerase de Naegleria gruberi (NgTIM) participa da via glicolítica, na qual atua na conversão de dihidroxiacetona fosfato em D-gliceraldeído-3-fosfato. Atualmente, a TIM mais semelhante com estrutura 3D relatada é a da planta Arabidopsis thaliana, que possui 58% de identidade sequencial com a NgTIM. A proteína recombinante NgTIM foi expressa em E. coli BL21(DE3), purificada por cromatografias de afinidade e exclusão de tamanho e cristalizada pelo método de difusão de vapor. Os melhores cristais foram obtidos em 3 diferentes condições, sendo aquele que proveu o melhor conjunto de dados em etanol 15% (V/V) e propoxilato pentaeritrol 40% (V/V). Dados de difração de raios X foram coletados para este cristal a 2,64 Å de resolução e processados. Ele pertence ao grupo de espaço P4 1 22 e têm parâmetros de cela unitária a = 79,70, c = 98,11 Å. A unidade assimétrica contém um monômero, com V M de 2,68 Å 3 Da-1 e um conteúdo de solvente de 54,2 %.

Recebido em 24/6/11; aceito em 27/11/11; publicado na web em 20/1/12 SURFACE ENERGY FOR (001) TiO 2 NANOSURFACES. In this work was made an investigation about bulk and surface models (at maximum 20 layers) of the TiO 2 material in the (001) direction. TiO 2 commercial sample was feature using XDR technique to determine phase and crystallites average size. Bulk and (001) surface models were simulated for TiO 2 material using DFT/B3LYP and its results were used for calculating energy surface, electronic levels, superficial atomic displacement and charge maps. Atoms of the first and second layers of the slab model showed electronic densities very well organized in the form of chains or wires.

RecA is a multifunctional protein that plays a central role in DNA repair in bacteria. The structural Make ATP Work motif (MAW) is proposed to control the ATPase activity of RecA. In the present work, we report the biochemical activity and structural effects of the L53Q mutation at the MAW motif of the RecA protein from H . seropedicae (HsRecA L53Q). In vitro studies showed that HsRecA L53Q can bind ADP, ATP, and ssDNA, as does wild-type RecA. However, the ATPase and DNA-strand exchange activities were completely lost. In vivo studies showed that the expression of HsRecA L53Q in E . coli recA 1 does not change its phenotype when cells were challenged with MMS and UV. Molecular dynamics simulations showed the L53Q point mutation did not cause large conformational changes in the HsRecA structure. However, there is a difference on dynamical cross-correlation movements of the residues involved in contacts within the ATP binding site and regions that hold the DNA binding sites. Additionally, a new hydrogen bond, formed between Q53 and T49, was hypothesized to allow an independent motion of the MAW motif from the hydrophobic core, what could explain the observed loss of activity of HsRecA L53Q.

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