FocAStrep–N was purified in a single step using a Strep-Tactin matrix (Fig. 2a), with a yield of approximately 1 mg of purified FocAStrep–N per liter of culture.

As observed in Western blots, purified FocAStrep–N migrated with a mass of ∼23 kDa in SDS-PAGE. Previous detailed topological analysis of FocA predicted the protein to have six transmembrane α-helices (Suppmann & Sawers, 1994). A CD spectrum of purified FocAStrep–N revealed that it is mainly α-helical in structure (Fig. 3). The characteristic twin troughs at 208 and 220 nm, as well as the high value at 195 nm of the spectrum, indicate a high α-helical content for FocA. Based on the CD spectrum shown in Fig. 3, the cdnn algorithm (Böhm et al., 1992) calculated the α-helical content of FocAStrep–N to be 52–56%. BN-PAGE is a method that has been developed EPZ015666 mouse to examine membrane–protein complexes and to estimate

their size (Schägger & von Jagow, 1991). Analysis of purified FocAStrep–N and FocAStrep–C by BN-PAGE showed that it migrated as a single species with a molecular mass of approximately 160–170 kDa (Fig. 2b). This indicates that it is oligomeric and forms either pentamers (using the deduced subunit molecular mass of 31 kDa) or heptamers/octamers (using the mass of 23 kDa in SDS-PAGE). Based on the fact Ruxolitinib mouse that the method is specifically designed for estimation of the size of membrane proteins, we suggest that FocAStrep–N is a pentamer. Western blotting with anti-FocA antibodies failed to detect any other abundant oligomeric form of the purified protein and confirmed its pentameric structure (Fig. 2c). Our immunological studies have revealed that FocA is not an abundant protein in E. coli growing by fermentation, and based on its unexpected pentameric structure, we calculate that there are roughly 100 oligomers per cell. This suggests that the protein must be efficient in formate transport. The overproduced protein was active in E. coli cells. Purification of FocA to near homogeneity was achieved and in quantities sufficient to allow a future

detailed biochemical characterization of the mechanism of formate transport. aminophylline This is the first reported purification of an FNT family member and should pave the way for future biochemical and biophysical analysis of this ancient family of small-molecule transporters. This work was supported by the Deutsche Forschungsgemeinschaft Graduiertenkolleg 1026 ‘Conformational transitions in macromolecular interactions. “
“Recently, a cyclic AMP receptor protein homologue, GlxR, was reported to bind to the upstream regions of several genes involved in the regulation of diverse physiological processes in Corynebacterium glutamicum. However, the function of GlxR has not yet been explored in C. glutamicum in vivo using a glxR deletion mutant.