Cloning, overexpression and purification of Bacillus subtilis elongation factor Tu in Escherichia coli

Structure and function of seed storage proteins in faba bean (Vicia faba L.)

The protein subunit is the most important basic unit of protein, and its study can unravel the structure and function of seed storage proteins in faba bean. In this study, we identified six specific protein subunits in Faba bean (cv. Qinghai 13) combining liquid chromatography (LC), liquid chromatography-electronic spray ionization mass (LC-ESI-MS/MS) and bio-information technology. The results suggested a diversity of seed storage proteins in faba bean, and a total of 16 proteins (four GroEL molecular chaperones and 12 plant-specific proteins) were identified from 97-, 96-, 64-, 47-, 42-, and 38-kD-specific protein subunits in faba bean based on the peptide sequence. We also analyzed the composition and abundance of the amino acids, the physicochemical characteristics, secondary structure, three-dimensional structure, transmembrane domain, and possible subcellular localization of these identified proteins in faba bean seed, and finally predicted function and structure. The three-dimensional structures were generated based on homologous modeling, and the protein function was analyzed based on the annotation from the non-redundant protein database (NR database, NCBI) and function analysis of optimal modeling. The objective of this study was to identify the seed storage proteins in faba bean and confirm the structure and function of these proteins. Our results can be useful for the study of protein nutrition and achieve breeding goals for optimal protein quality in faba bean.

Self-inducible Bacillus subtilis expression system for reliable and inexpensive protein production by high-cell-density fermentation

A novel technically compliant expression system was developed for heterologous protein production in Bacillus subtilis with the aim of increasing product yields at the same time as decreasing production costs. Standard systems involve the positively regulated manP promoter of the mannose operon, which led to relatively high product yields of 5.3% (5.3 g enhanced green fluorescent protein [eGFP] per 100 g cell dry weight [CDW]) but required large quantities of mannose to induce the reactions, thus rendering the system's technical application rather expensive. To improve this situation, mutant B. subtilis strains were used: the ΔmanA (mannose metabolism) strain TQ281 and the ΔmanP (mannose uptake) strain TQ356. The total amount of inducer could be reduced with TQ281, which, however, displayed sensitivity to mannose. An inducer-independent self-induction system was developed with TQ356 to further improve the cost efficiency and product yield of the system, in which glucose prevents induction by carbon catabolite repression. To create optimal self-induction conditions, a glucose-limited process strategy, namely, a fed-batch process, was utilized as follows. The initiation of self-induction at the beginning of the glucose-restricted transition phase between the batch and fed-batch phase of fermentation and its maintenance throughout the glucose-limiting fed-batch phase led to a nearly 3-fold increase of product yield, to 14.6%. The novel B. subtilis self-induction system thus makes a considerable contribution to improving product yield and reducing the costs associated with its technical application.

Bacterial elongation factors EF-Tu, their mutants, chimeric forms, and domains: isolation and purification

Prokaryotic elongation factors EF-Tu form a family of homologous, three-domain molecular switches catalyzing the binding of aminoacyl-tRNAs to ribosomes during the process of mRNA translation. They are GTP-binding proteins, or GTPases. Binding of GTP or GDP regulates their conformation and thus their activity. Because of their particular structure and regulation, various activities (also outside of the translation system) and a relative abundance they represent attractive tools for studies of many basic but still not fully understood mechanisms both of the translation process, the structure-function relationships in EF-Tu molecules themselves and proteins and energy transduction mechanisms in general. The review critically summarizes procedures for the isolation and purification of native and engineered eubacterial elongation factors EF-Tu and their mutants on a large as well as small scale. Current protocols for the purification of both native and polyHis-tagged or glutathione-S-transferase (GST)-tagged EF-Tu proteins and their variants using conventional procedures and the Ni-NTA-Agarose or Glutathione Sepharose are presented.

Isolation of chimaeric forms of elongation factor EF-Tu by affinity chromatography

Six different recombinant chimaeric forms of a three-domain protein, proteosynthetic elongation factor Tu (EF-Tu), composed of domains of EF-Tu of mesophilic (Escherichia coli) and thermophilic (Bacillus stearothermophilus) origin as well as free N-terminal domains of EF-Tu, and the whole recombinant EF-Tus of both organisms were prepared and isolated by the GST (glutathione S-transferase) fusion technology. Several modifications in the standard isolation and purification procedures are described that proved necessary to obtain the proteins in a purified and undegraded form.

Efficient separation of Thermus aquaticus EF-Tu functional complexes

A new method for fast separation of the main functional complexes of the elongation factor Tu from Thermus aquaticus has been developed. Binary complexes EF-Tu * GDP and EF-Tu * GDPNP as well as the ternary complex EF-Tu * GDPNP * Leu approximately tRNA were separated from each other by means of HPLC on a hydrophobic sorbent TSK-Gel Phenyl 5PW in a reverse gradient of ammonium sulfate. This technique is suitable for monitoring EF-Tu activity, characterisation of the ratio between different EF-Tu forms in cell extracts, and isolation of individual EF-Tu complexes for structural and functional investigations. In order to illustrate the potentials of the method, we used HPLC on a TSK-Gel Phenyl 5PW matrix to determine the ratio between affinities of GDP and GDPNP for EF-Tu. We found that K(a)(GDP) is about 27 times higher than K(a)(GDPNP) at 37 degrees C, the value being close to the one reported for Thermus thermophilus EF-Tu.