BIOPHYSICS AND COMPUTATIONAL BIOLOGY Correction for “SNARE machinery is optimized for ultrafast fusion,” by Fabio Manca, Frederic Pincet, Lev Truskinovsky, James E. Rothman, Lionel Foret, and Matthieu Caruel, which was first published January 30, 2019; 10.1073/pnas.1820394116 (Proc. Natl. Acad. Sci. U.S.A. 116, 2435–2442).
The authors wish to note the following: “The results published in this article were obtained with a set of parameters slightly different from the one indicated in Table 1. This led to an incorrect Fig. 2 A–C. There was also a typo in the value of parameter κn, which was supposed to be 1.5 pN nm–1 in Table 1. The corrections made do not affect in any way our estimate of the time to pass the fusion barrier (τ2), and only slightly modify the N dependence of τ1. Hence, the main conclusion of our paper, the existence of an optimal number of SNAREpins between 3 and 6 units, which guarantee submillisecond fusion times, remains unaltered.
Table 1.
Physical parameters adopted in the model and references
| Parameter | Symbol | Value | Units | Source |
| Zipping distance | a | 7 | nm | Ref. 1 |
| Energy bias | e0 | 28 | kBT | Ref. 1 |
| Fully zipped stiffness | κc | 12 | pN nm−1 | SI Appendix |
| Half-zipped stiffness | κn | 1.5 | pN nm−1 | SI Appendix |
| Maximum zippering rate | k | 1 | MHz | Ref. 1 |
| Drag coefficient | η | 3.8 × 10−7 | N s m−1 | |
| FB position | yf | 2 | nm | Refs. 2 and 3 |
| FB width | σf | 0.3 | nm | Refs. 4 and 5 |
| FB height | ef | 26 | kBT | Refs. 6 and 7 |
FB, fusion barrier. 1 kBT ≈ 4 zJ.
Fig. 2.
Main results. (A and B) Typical stochastic trajectories of the intermembranes distance y(t) (A) and the number Nc(t) of SNAREpins in state c (B) obtained from the numerical simulations. The insets in A and B show magnification of the trajectories in the time interval (43 μs, 45 μs). (C) Average of the waiting times τ1 (black), τ2 (blue), and τfusion = τ1 + τ2 (red) obtained from the numerical simulations (symbols) and our effective chemical model (lines). The numerical values corresponding to τfusion obtained in ref. 8 are represented by the red dashed line. (D) Effective free energy landscape Φ showing the three stages of fusion and the associated transition rates. Parameters are listed in Table 1.
The proposed analytic approximations are still able to accurately reproduce the exponential dependence of the timescales τ1 and τ2 on the number of SNAREpins N; see Eqs. 5 and 6 in this article. However, with the updated set of parameters, the analytical estimate for the prefactor in Eq. 6 is underestimated.” The corrected Fig. 2, legend for Fig. 2, and Table 1 appear below.
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