Lipid rafts are cholesterol-enriched microdomains and implicated in many essential physiological ac-tivities such as the neurotransmitter release.Many studies have been carried out on the function of rafts inthe plasma membranes,whereas little is known about the information of such microdomains in subcellularcompartments especially synaptic vesicles(SVs).In the well-studied plasma membranes,several proteinshave been recognized as raft markers,which are used to label or trace rafts.But the raft marker proteinon SVs has not been identified yet.Although some SV proteins,including VAMP and CPE,have beenfound in raft fractions,they cannot be used as markers due to their low abundance in rafts.In this work,we designed several chimera proteins and tested their characteristics for using as SV raft makers.First,we detected whether they located in SVs,and then the chimeras exhibiting the better localization in SVswere further examined for their enrichment in raft using detergent treatment and gradient density floatationanalysis.Our results indicate that one of the chimeric proteins is primarily located in SVs and distributedin raft microdomains,which strongly suggests that it could be served as a raft marker for SVs.
SecA is the essential component of the signal-peptide dependent translocation pathway in Escherichia coil （E.coh）. The structure and function of SecA must be known to understand the molecular mechanism of preprotein translocation. The high flexibility of SecA causes a dynamic conformational heterogeneity which presents a barrier to the growth of crystals of high diffraction quality. Electron microscopy was used to resolve the macromolecular structure of SecA in solution by negative staining and single particle analysis at a resolution of 2.9 nm. The structure of E. coil SecA is similar to the dimeric form of Bacillus subtilis SecA and is 10 nm × 10 nm × 5 nm in size.
