Terauchi san :
@Science issue 6021: A sorting platform determines the order of protein secretion in bacterial type III system
Type III protein secretion systems (T3SSs) are specialized complexes of molecules in Gram-negative bacteria that mediate the introduction of virulence proteins directly into eukaryotic host cells. The proper function of these systems depends on sequential secretion of the needle components. However, how this hierarchical process is regulated has been unclear. In this paper, they report a mechanism by which a type III secretion system from the bacterial enteropathogen Salmonella enterica serovar typhimurium can sort its substrates before secretion. A cytoplasmic component of T3SS, SpaO is a key player in controlling sequential secretion of proteins and it forms a high molecular weight complex, The SpaO-OrgA-OrgB might dock the translocases, 'poised' for secretion upon host cell contact.
Science issue 6021: Three-dimensional model of salmonella's needle complex at subnanometer resolution.
This paper analyzes the top view of NCs or NC substructures from Salmonella typhimurium by cryo-electron microscopy images. It showed that they formed a 24-fold symmetry for the inner rings and 15-fold symmetry for the outer rings, giving an overall C3 symmetry. They also found the most rigid part of NC is composed of the IR1, the periplasmic localized domain of the IR and the connection between the outer ring and the neck. The flexible part of the core NC was at IR2 and the connection between the outer ring and the neck. They also docked the near-atomic models of the IR1 and the neck region. IR have the extensive structural deviations, which might reflect different conformational or even compositional stated. This suggested that IR2 in fact plays an additional functional role during secretion, for example, as a binding platform for a putative C ring.
Kingo san:
PNAS Vol. 108, No.5: Membrane lipidome of an epithelial cell line.
They used madin-Darby canine kidney cell as model for epithelium formation and investigated the remodeling of the total cell membrane lipidome during the transition from a nonpolarized morphology to an epithelial morphology and vice versa by shotgun-based lipidomics workflow. They optimized the two-stage lipid extraction. Using a combination of TLC and shotgun MS. They demonstrated enhanced recovery of the major mammalian GSPs and their detection at the low picomole level within a dynamic range better than 100X. They observed pronounced changes in the abundance of DAG as well as in the remodeling of PE and SP composition. Furthermore, they found a gradual remodeling of lipid species profiles during epithelial polarization.