Table 1.

Properties of the neuronal template complex cross-linked at X-8 or X-6 containing syntaxin-1 (Syx) or Munc18-1 (M18) modifications

Cross-linking site	Syx or M18 modification	Template complex		Munc18-1-bound open syntaxin†		SNAP-25 binding (60 nM)
		Unfolding energy (kBT)	Equilibrium force* (pN)	Unfolding energy (kBT)	Equilibrium force (pN)	Prob.‡	N§
X-8		WT	5.2 (0.1)	5.1 (0.1)	2.6 (0.2)	10.8	0.27	55
	Syx Δ147-197	4.7 (0.2)	5.4 (0.2)	2.7 (0.3)	11.1 (0.4)	0	18
	Syx Δ147-170	4.8 (0.2)	5.2 (0.1)	3.0 (0.2)	10.3 (0.1)	0.24	29
	M18 GS314-326	N.D.	N.A.	2.7 (0.2)	10.6 (0.1)	0	14
	M18 Δ314-326	N.D.	N.A.	N.D.	N.A.	0	22
X-6	WT	3.9 (0.1)	5.8 (0.1)	2.4 (0.2)	11.4 (0.2)	0.035	50
	Syx Δ147-197	3.5 (0.1)	6.1 (0.1)	2.4 (0.2)	12.6 (0.2)	0.029	11
	Syx M183A	3.7 (0.2)	6.2 (0.1)	2.2 (0.2)	11.5 (0.2)	0.047	21
	Syx D184P	3.5 (0.2)	6.3 (0.2)	1.9 (0.2)	10.8 (0.3)	0.056	18
	M18 GS314-326	N.D.	N.A.	2.3 (0.2)	10.3 (0.3)	0	19
	M18 Δ314-326	N.D.	N.A.	N.D.	N.A.	0	29
	Syx LE/ M18 D326K	4.5 (0.2)	6.7 (0.1)	2.1 (0.2)	11.5 (0.2)	0.029	34

The number in parenthesis is the SEM. N.D., not detected, which means that the stability of the template complex is too weak to be detected by our method, estimated to be <1.5 k_BT. N.A., not available.

^*Mean of two average forces for the unfolded and folded states when the two states are equally populated (38). The equilibrium force of the template complex generally correlates with its unfolding energy.

^†Detected as the syntaxin- and Munc18-1-dependent transition in the force range of 10 to 15 pN.

^‡Probability of SNAP-25B binding to the template complex per relaxation.

^§Total number of relaxations to detect SNAP-25 binding.