Inclusion bodies: not that bad .

The formation of inclusion bodies (IBs) constitute a frequent event during the production of heterologous proteins in bacterial hosts. Although the mechanisms leading to their formation are not completely understood, empirical data have been exploited trying to predict the aggregation propensity of specific proteins while a great number of strategies have been developed to avoid the generation of IBs. However, in many cases, the formation of such aggregates can be considered an advantage for basic research as for protein production. In this review, we focus on this positive side of IBs formation in bacteria. We present a compilation on recent advances on the understanding of IBs formation and their utilization as a model to understand protein aggregation and to explore strategies to control this process. We include recent information about their composition and structure, their use as an attractive approach to produce low cost proteins and other promising applications in Biomedicine.

A high resolution analysis of the structure and chemical composition of the calcareous corpuscles from Mesocestoides corti.

Mesocestoides corti (syn. vogae), similar to many other cestode platyhelminthes, contains abundant calcium carbonate structures called calcareous corpuscles. These concretions that may constitute as much as 40% of the dry weight of the body, and were proposed to form intracellularly in certain parenchymal cells. As an approach to elucidate the biological role of calcareous corpuscles in cestodes, our aim was to characterize more precisely the structure and topological composition of the corpuscles from M. corti. Employing a variety of high resolution technical approaches, we found that the calcareous corpuscles are spheroid or ovoid layered concretions. They are formed by topographically homogeneous but compositionally heterogeneous layers, suggesting a cyclic process of biomineralization. The layers are composite structures, with granules of tens of nanometers, each surrounded by a cortex of about eight nanometers.

Monohydrocalcite in calcareous corpuscles of Mesocestoides corti.

Mesocestoides corti (syn. vogae), as many other cestode platyhelminthes, contains abundant mineralized structures called calcareous corpuscles. These concretions may constitute as much as 40% of the dry weight of the organisms, but their function remains poorly understood. In this work, we reviewed the mineral composition of the calcareous corpuscles of M. corti. X-ray diffraction pattern showed that the major mineral component of the corpuscles is a hydrated form of calcium carbonate, monohydrocalcite, also confirmed by infrared spectrometry. The baseline shift of the X-ray diffraction spectra suggested the presence of amorphous calcium carbonate, accordingly to previous reports, and an organic matrix was confirmed by FTIR. Monohydrocalcite is a rare mineral unusually found in biominerals. Although the significance of monohydrocalcite in biominerals has not been determined, the knowledge of corpuscles composition is of relevance to establish their function and for the elucidation of the mechanisms involved in mineralization processes.

Translational machinery and protein folding: evidence of conformational variants of the estrogen receptor alpha.

As an approach to understand how translation may affect protein folding, we analyzed structural and functional properties of the human estrogen receptor alpha synthesized by different eukaryotic translation systems. A minimum of three conformations of the receptor were detected using limited proteolysis and a sterol ligand-binding assay. The receptor in vitro translated in rabbit reticulocyte lysate was rapidly degraded by protease, produced major bands of about 34kDa and showed a high affinity for estradiol. In a wheat germ translation system, the receptor was more slowly digested. Two soluble co-existing conformations were evident by different degradation patterns and estradiol binding. Our data show that differences in the translation machinery may result in alternative conformations of the receptor with distinct sterol binding properties. These studies suggest that components of the cellular translation machinery itself might influence the protein folding pathways and the relative abundance of different receptor conformers.