Bioavailability of vitamin C from mashed potatoes and potato chips after oral administration in healthy Japanese men.

Potato (Solanum tuberosum) tubers contain vitamin C (VC) and commercial potato chips have more VC content per wet weight by dehydration during frying. However, intestinal absorption of VC from orally ingested potatoes and its transfer to the blood remains questionable. The present study was designed to determine whether the dietary consumption of potatoes affects VC concentration in plasma and urinary excretion of VC in human subjects.

Improvement of multiple-stress tolerance and lactic acid production in Lactococcus lactis NZ9000 under conditions of thermal stress by heterologous expression of Escherichia coli DnaK.

The effects of nisin-induced dnaK expression in Lactococcus lactis were examined, and this expression was shown to improve stress tolerance and lactic acid fermentation efficiency. Using a nisin-inducible expression system, DnaK proteins from L. lactis (DnaK(Lla)) and Escherichia coli (DnaK(Eco)) were produced in L.

The proper ratio of GrpE to DnaK is important for protein quality control by the DnaK-DnaJ-GrpE chaperone system and for cell division.

A balance of the intracellular concentrations of molecular chaperones in response to environmental conditions is of considerable importance for cellular homeostasis. Here, the physiological consequences of overexpression of GrpE in wild-type Escherichia coli MC4100 were examined. Overexpression of GrpE resulted in defects in cell division and growth, but overexpression of GrpE-G122D, which carries the G122D point mutation resulting in impaired interaction with DnaK, did not; this indicated that the effect of GrpE overexpression could be related to the DnaK chaperone function.

Construction of Escherichia coli dnaK-deletion mutant infected by lambdaDE3 for overexpression and purification of recombinant GrpE proteins.

Escherichia coli is widely employed to produce recombinant proteins because this microorganism is simple to manipulate, inexpensive to culture, and of short duration to produce a recombinant protein. However, contamination of molecular chaperone DnaK during purification of the recombinant protein is sometimes a problem, since DnaK sometimes has a negative effect on subsequent experiments. Previously, several efforts have been done to remove the DnaK contaminants by several sequential chromatography or washing with some expensive chemicals such as ATP.

In vivo and in vitro complementation study comparing the function of DnaK chaperone systems from halophilic lactic acid bacterium Tetragenococcus halophilus and Escherichia coli.

In this study, we characterized the DnaK chaperone system from Tetragenococcus halophilus, a halophilic lactic acid bacterium. An in vivo complementation test showed that under heat stress conditions, T. halophilus DnaK did not rescue the growth of the Escherichia coli dnaK deletion mutant, whereas T.

A gram-negative characteristic segment in Escherichia coli DnaK is essential for the ATP-dependent cooperative function with the co-chaperones DnaJ and GrpE.

We describe importance of the characteristic segment in ATPase domain of DnaK chaperone which is present in all gram-negative bacteria but is absent in all gram-positive bacteria. In vitro studies, ATPase activity, luciferase-refolding activity, and surface plasmon resonance analyses, demonstrated that a segment-deletion mutant DnaKDelta74-96 became defective in the cooperation with the co-chaperones DnaJ and GrpE. In addition, in vivo complementation assay showed that expression of DnaKDelta74-96 could not rescue the viability of Escherichia coli DeltadnaK mutant at 43 degrees C.