RESUMO
The efficiency of Helicobacter pylori as a mucosal pathogen is caused by unique soluble and integral membrane proteins, which allow its survival at acidic pH and successful colonization of the gastric environment. With about one-fourth of the H. pylori's proteome comprising integral membrane proteins, the need for solution of their three-dimensional (3D) structures becomes persistent as it can potentially drive the generation of more effective drugs. This study presents a medium-throughput approach for cloning and expression screening of integral membrane proteins from H. pylori (26695) using Escherichia coli as the expression host. One-hundred sixteen H. pylori targets were cloned into two different vector systems and heterologously expressed in E. coli. Eighty-four percent of these proteins displayed medium to high expression. No clear-cut correlation was found between expression levels and number of putative transmembrane spans, predicted functionality, and molecular mass. Nonetheless, expression of transporters and hypothetical proteins < or =40 kDa with two to four transmembrane spans displayed generally high expression levels. To statistically strengthen the quality of the data from the medium-throughput approach, a comparison with data derived from robotic-based methodologies was conducted. Optimization of expression and solubilization conditions for selected targets was also performed. Seventeen targets have been purified and subjected to crystallization so far. Eighteen percent of these targets (2/17) produced crystals under specific sets of crystallization conditions.
