Publications by authors named "Thomas L Torng"

2 Publications

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Sec17/Sec18 can support membrane fusion without help from completion of SNARE zippering.

Elife 2021 May 4;10. Epub 2021 May 4.

Department of Biochemistry and Cell Biology Geisel School of Medicine at Dartmouth, Hanover, United States.

Membrane fusion requires R-, Qa-, Qb-, and Qc-family SNAREs that zipper into RQaQbQc coiled coils, driven by the sequestration of apolar amino acids. Zippering has been thought to provide all the force driving fusion. Sec17/αSNAP can form an oligomeric assembly with SNAREs with the Sec17 C-terminus bound to Sec18/NSF, the central region bound to SNAREs, and a crucial apolar loop near the N-terminus poised to insert into membranes. We now report that Sec17 and Sec18 can drive robust fusion without requiring zippering completion. Zippering-driven fusion is blocked by deleting the C-terminal quarter of any Q-SNARE domain or by replacing the apolar amino acids of the Qa-SNARE that face the center of the 4-SNARE coiled coils with polar residues. These blocks, singly or combined, are bypassed by Sec17 and Sec18, and SNARE-dependent fusion is restored without help from completing zippering.
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http://dx.doi.org/10.7554/eLife.67578DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8143792PMC
May 2021

Line Tension Controls Liquid-Disordered + Liquid-Ordered Domain Size Transition in Lipid Bilayers.

Biophys J 2017 Apr;112(7):1431-1443

Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York. Electronic address:

To better understand animal cell plasma membranes, we studied simplified models, namely four-component lipid bilayer mixtures. Here we describe the domain size transition in the region of coexisting liquid-disordered (Ld) + liquid-ordered (Lo) phases. This transition occurs abruptly in composition space with domains increasing in size by two orders of magnitude, from tens of nanometers to microns. We measured the line tension between coexisting Ld and Lo domains close to the domain size transition for a variety of lipid mixtures, finding that in every case the transition occurs at a line tension of ∼0.3 pN. A computational model incorporating line tension and dipole repulsion indicated that even small changes in line tension can result in domains growing in size by several orders of magnitude, consistent with experimental observations. We find that other properties of the coexisting Ld and Lo phases do not change significantly in the vicinity of the abrupt domain size transition.
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http://dx.doi.org/10.1016/j.bpj.2017.02.033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390056PMC
April 2017