Quorum sensing (QS), or cell-to-cell communication in bacteria, is achieved through the production and subsequent response to the accumulation of extracellular signal molecules called autoinductors. The main role of QS is regulation of production of virulence factors in bacteria. Bacterial pathogenicity is often manifested by the expression of various cell-associated and secreted virulence factors, such as exoenzymes, toxins and biofilm. In bacteria, the expression of virulence factors is controlled coordinately by the global regulatory QS systems, which includes the AI-1/LuxIR-, AI-2/LuxS-, AI-3/QsC-, AIP/Agr-based systems. The regulation of production of virulence factors is extremely complex and many components influence it.
An active form of p38 protein kinase, belonging to the mitogen-activated protein kinases subfamily, has been designed based on crystallographically known structures of two other kinases, an active form of protein kinase A (PKA) and an inactive form of extracellular signal-regulated kinase 2 (ERK2). The modelling procedure is described. Its general scheme can also be applied to other kinases. The structure of the active forms of p38 and PKA is very similar in the region which binds the substrate. The ATP-binding mode is very similar in the active forms of all the three studied kinases. Models of the active forms allow for further studies on transphosphorylation processes at the molecular level, and modelling of inhibitors competitive with ATP and/or substrates.
4
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Performance of mucosal epithelial barrier is modified by numerous agents that exert effects on mucin-Mucin Binding Protein (MBP)complex.The aim of the studies described was to determine the nature of the damage or modification of oral mucous barrier by the short-term exposure to ethanol.Methods:Culture of rat buccal mucosa in the presence of ethanol and [3H]-labeled proline and palmitate revealed substantial decrease in MBP synthesis and the release of MBP to the medium.The radioscanning of the samples prepared from the culture medium and the apical epithelial membranes subjected to SDS- PAGE and western blotting disclosed that the released,water soluble 97kDa MBP glycopeptide was labeled with proline and palmitate.When the experiments were conducted in the presence of 5mM EDTA,the GPI-PLD inhibitor,the majority of radiolabeled MBP remained in the membrane-bound form and was extractable with Triton X-114.The results on the purified GPI-linked MBP degradation by serum enzyme,by the saliva containing serum transudate,and the suppression of the process by inclusion of GPI-PLD-specific inhibitor support our contention that membrane MBP is released to medium by GPI-PLD- like activity.Results:The release of MBP from apical epithelial surfaces was induced by depletion of mucin and the presence of serum-derived GPI-PLD in the tissue homogenate. Strong likelihood exists that under in situ conditions ethanol-induced transudation of serum to saliva provides the vehicle for the transfer of GPI-PLD activity to salivary contents. Defacement of the oral surfaces from mucous barrier signals prospect of lumenal agent influence on the unprotected epithelial exterior,and allows ingression of microbes and untoward acting substances into the organism.