Biophysical dissection of schistosome septins: Insights into oligomerization and membrane binding.
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 and SmSEPT10 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 of SmSETP10, 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.
Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
Ana Eliza
AE
Zeraik
Department of Physics, University of Durham, UK.
Margarita
M
Staykova
Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
Marina Gabriel
MG
Fontes
Department of Physics, University of Durham, UK.
Indrė
I
Nemuraitė
School of Biological and Biomedical Sciences, University of Durham, UK.
Roy
R
Quinlan
Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
Ana Paula Ulian
AP
Araújo
Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil. Electronic address: rdemarco@ifsc.usp.br.
Ricardo
R
DeMarco
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D055592:Biophysical Phenomena; D002942:Circular Dichroism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D005810:Multigene Family; D011485:Protein Binding; D055503:Protein Multimerization; D012550:Schistosoma mansoni / Q000235:genetics / Q000378:metabolism*; D058112:Septins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics
D015801:Helminth Proteins; D008081:Liposomes; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D058112:Septins
GTP binding protein; Protein-lipid interaction; Protein-protein interaction; Septin