, 2011). However, subsequent work using recombinant synuclein has confirmed that even the nondenatured recombinant protein is intrinsically disordered and loses its α-helical conformation after dissociation from membranes (Fauvet et al., 2012). Loss of helicity Tanespimycin could thus reflect the dilution inherent in preparing an

extract, with the helical state maintained at higher concentrations (Dettmer et al., 2013 and Wang et al., 2011), but NMR studies in E. coli have in fact suggested that macromolecular crowding maintains the disordered state of synuclein ( McNulty et al., 2006). It is also possible that synuclein folds to form a multimer only in mammalian cells, but the analysis of native brain synuclein has recently confirmed its almost entirely monomeric state ( Burré et al., 2013). Recently, it has also been shown that

synuclein can assemble into an oligomer (possibly tetramer) on nanoparticles ( Varkey et al., 2013), but this phenomenon seems to differ from the ability of a preformed tetramer to interact with membranes ( Wang et al., 2011). At this point, it remains possible that α-synuclein adopts a helical tetrameric state in solution, but the evidence is not definitive. The unavoidable dilution that accompanies purification of native synuclein complicates the analysis, but it is perhaps more important to acknowledge that despite extensive biochemical studies Selleck EGFR inhibitor in vitro, the conformation of synuclein in cells remains poorly

understood. In contrast to the N-terminal membrane binding domain, the C terminus of human α-synuclein is polar, with a higher proportion of charged residues. This domain undergoes almost phosphorylation at multiple sites (Oueslati et al., 2010 and Sato et al., 2013), suggesting a mechanism for regulation, but the function of the C terminus remains unclear, and it is the least conserved domain across species as well as among α-, β-, and γ- isoforms. The C terminus may affect membrane binding under particular conditions (Shvadchak et al., 2011), but phosphorylation toward the end of the N-terminal repeats, at Ser-87, more clearly affects membrane binding in vitro than phosphorylation at the other, more C-terminal sites (Paleologou et al., 2010). The observations thus suggest a potential biological role for Ser-87 phosphorylation, although this again remains to be identified in the context of the cell. The presynaptic location of α-synuclein has been recognized since its original identification as a protein associated with synaptic vesicles (Maroteaux et al., 1988). In contrast to many proteins involved in neurodegeneration that are distributed throughout the neuron, however, α-synuclein localizes specifically to the nerve terminal, with relatively little in the cell body, dendrites, or extrasynaptic sites along the axon (George et al., 1995 and Iwai et al., 1995).