An elevated OmpA expression during the production of a recombinant protein in Escherichia coli.

Escherichia coli cells rapidly respond to changes in the environment. Such response must be anticipated upon development of fermentation strategy for commercial purposes. The response may signal changes in cell physiology, which is critical for the cell growth and the level of the target protein production. One of the responses is the elevated expression of membrane proteins to tightly control the trafficking of molecules into and out from the cells. Normally, the expression level of the membrane protein is basal as the fermentation is carried out in physiological conditions. Here, we reported an elevated expression of the outer membrane protein A (OmpA) during a series of fermentation conduct, starting from the shake flask, 1-L to finally 10-L fermentor. The incidence led to a lower expression of the target protein and thereby resulting in lower process efficiency. OmpA expression was concomitant to the bacterial growth and already observed in the early exponential phase. Despite the drawback, this phenomenon actually inspires the observation of OmpA expression as one of the indicators for the E. coli cells response to the fermentation conditions. This auxiliary check would prevent the higher OmpA expression that led to the low expression of the target protein.

The role of S126 in the Staphylococcus equorum MnSOD activity and stability.

The dimeric form of manganese superoxide dismutase is instrumental for activity because each of the monomers provides amino acid residues participating in the enzymatic reaction. Hence, preventing dissociation of the dimer would maintain the enzymatic activity in detrimental conditions e.g. high temperature. To prevent dissociation of the dimer, a disulphide (S-S) bond was introduced at the dimer interface. In the wild type structure, S126 interacts with S126 of the other monomer. In the presented work, a mutant was designed with an S126C substitution. The crystal structure of the S126C mutant showed that only 50-70% of monomers formed the S-S bond. This observed imperfect S-S bonding was likely caused by photolytic S-S bond breakage mediated by the neighbouring tryptophan residue. In the wild type, S126 is located facing W163 and forms a water-mediated hydrogen bond with E164; W163 and E164 are crucial in the enzyme's activity. The replacement of S126 by a cysteine residue lowered the activity of the enzyme by ~70%. S126 has never been considered to play a role in the enzyme's activity or stability, thus the finding showed the importance of this residue.

Agaricus bisporus mannose binding protein is not an agglutinating protein.

Agaricus bisporus mannose binding protein (Abmb) demonstrates permeability to epithelial monolayer barrier of the intestine, resistance to gastrointestinal tract conditions and to proteolysis therefore it holds potential as a drug carrier for oral route administration. Abmb also display antiproliferative activity to breast cancer cells and stimulation of immune system thus could potentially be also developed for therapeutic purpose. It is not immunogenic or toxic thereby safe for use. In this paper we further provide evidence that Abmb also lacks of agglutinating activity despite sharing high structural homology to lectins. Abmb is thereby the only mannose specific binding protein that is not member of lectin family. This evidence provides further support on the use of Abmb as pharmaceutical or medicinal agent. Its molecular globularity that may contribute to its lack of agglutination capacity was also evaluated.