Open Access Research article

Network motif comparison rationalizes Sec1/Munc18-SNARE regulation mechanism in exocytosis

Tian Xia1*, Jiansong Tong2, Shailendra S Rathore3, Xun Gu45 and Julie A Dickerson5*

Author Affiliations

1 Biomedical Informatics Center, Northwestern University, Chicago, IL 60611, USA

2 Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA

3 Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, Boulder, CO 80309, USA

4 Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA

5 Program of Bioinformatics and Computational Biology, Iowa State University, Ames, IA 50011, USA

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BMC Systems Biology 2012, 6:19  doi:10.1186/1752-0509-6-19

Published: 16 March 2012



Network motifs, recurring subnetwork patterns, provide significant insight into the biological networks which are believed to govern cellular processes.


We present a comparative network motif experimental approach, which helps to explain complex biological phenomena and increases the understanding of biological functions at the molecular level by exploring evolutionary design principles of network motifs.


Using this framework to analyze the SM (Sec1/Munc18)-SNARE (N-ethylmaleimide-sensitive factor activating protein receptor) system in exocytic membrane fusion in yeast and neurons, we find that the SM-SNARE network motifs of yeast and neurons show distinct dynamical behaviors. We identify the closed binding mode of neuronal SM (Munc18-1) and SNARE (syntaxin-1) as the key factor leading to mechanistic divergence of membrane fusion systems in yeast and neurons. We also predict that it underlies the conflicting observations in SM overexpression experiments. Furthermore, hypothesis-driven lipid mixing assays validated the prediction.


Therefore this study provides a new method to solve the discrepancies and to generalize the functional role of SM proteins.