Title
Biophysical dissection of schistosome septins: insights into oligomerization and membrane binding
Author
Ana Eliza Zeraik, Margarita Staykova, Marina Gabriel Fontes, Indrė Nemuraitė, Roy Quinlan, Ana Paula Ulian Araújo, Ricardo DeMarco
Year
2016
Journal
Biochimie
Abstract
Septins are GTP-binding proteins that are highly conserved among eukaryotes and which are usually membrane-associated. They have been linked to several critical cellular functions such as exocytosis and ciliogenesis, but little mechanistic detail is known. Their assembly into filaments and membrane binding properties are incompletely understood and that is specially so for non-human septins where such information would offer therapeutic potential. In this study we use Schistosoma mansoni, exhibiting just four septin genes, as a simpler model for characterizing the septin structure and organization. We show that the biochemical and biophysical proprieties of its SmSEPT5 andSmSEPT10 septins are consistent with their human counterparts of subgroups SEPT2 and SEPT6, respectively. By succeeding to isolate stable constructs comprising distinct domains of SmSEPT5 and SmSEPT10 we were able to infer the influence of terminal interfaces in the oligomerization and membrane binding properties. For example, both proteins tended to form oligomers interacting by the N- and C-terminal interfaces in a nucleotide independent fashion but form heterodimers via the G interface, which are nucleotide dependent. Furthermore, we report for the first time that it is the C-terminus ofSmSETP10, rather than the N-terminal polybasic region found in other septins, that mediates its binding to liposomes. Upon binding we observe formation of discrete lipo-protein clusters and higher order septin structures, making our system an exciting model to study interactions of septins with biological membranes.
Instrument
J-815
Keywords
Circular dichroism, Secondary structure, Chemical stability, Biochemistry