The three proteins with amino acid substitutions of this study were tested for their abilities to protect membranes from thermal damage. Interestingly, Y107A was associated with the membrane, but appeared to have an impaired capacity to stabilize membranes, in contrast to the other proteins. It has been described previously that dissociation of the oligomer is a prerequisite for the Hsp16.3 membrane-association process (Zhang et al., 2005). It has also been suggested that Hsp16.3 dissociates into
selleck chemicals small oligomers to expose certain interfaces that are necessary for the membrane-association process that follows (Zhang et al., 2005). Although the Y107A did not prevent interaction with the membrane, the membrane stabilization activity was abolished. Consequently, we suggest that the amino acid in position 107 may be necessary for this activity or/and for correct insertion at the membrane level. Our Tanespimycin data presented here strongly suggest that the amino acids involved in chaperone activity on denaturated proteins
and membrane fluidity regulation are different and are localized in the α-crystallin domain. However, we cannot exclude the existence of amino acids necessary for both activities. The construction and characterization of other proteins with amino acid substitutions should help to understand how Lo18 is able to function on both substrates. This study was supported by the Ministère de l’Education Nationale de la Recherche et de la Technologie and the Université de Bourgogne. We thank M. Guillemin and D. Carrel for their technical assistance and L. Gal for his help in point substitutions of Lo18. We thank Alex Edelman and associates for their reading of the English text. “
“Staphylococcus aureus is a common human pathogenic bacteria that can cause serious infections, including lethal staphylococcal pneumonia. The development of antimicrobial
resistance has limited treatment options for this pathogen; consequently, novel antibiotics and strategies not are urgently desired to combat these infections. In recent years, virulence factors secreted by pathogenic microorganisms have been developed as targets for drug discovery. Alpha-hemolysin, a pore-forming cytotoxin that is secreted by most S. aureus strains, is essential for the pathogenesis of S. aureus pneumonia. In this study, we report that apigenin, a compound extracted from parsley that has no antimicrobial activity vs. S. aureus in vitro, can remarkably decrease the production of α-hemolysin at low concentrations. When added to the A549 cells and S. aureus co-culture system, apigenin protected A549 cells from α-hemolysin-mediated injury. Furthermore, in vivo tests indicated that apigenin alleviated injury of the lung tissue and decreased cytokine levels in the bronchoalveolar lavage fluid in the mouse model of S. aureus pneumonia.