Table II. Rate constants for... | Rockefeller University Press

Table II.

Rate constants for phosphoinositide metabolism

Parameter	Value	Units	Rationale
k_PLC	0.1	µm² s⁻¹	Oxo-M onset of current inhibition
k_PLConPIP	0.14 * k_PLC	µm² s⁻¹	See Horowitz et al. (2005)
k_PLCbasal	0.0025	s⁻¹	To keep resting IP₃ at 0.16 µM
k_4K	2.6 × 10⁻⁴	s⁻¹	Current recovery after Oxo-M
k_4P	0.006	s⁻¹	To keep PI(4)P levels stable at rest
k_5K	0.02	s⁻¹	Current recovery after VSP
k_5P	0.014	s⁻¹	To keep PIP₂ levels stable at rest
k_VSP^a	11.3 * f(V)	s⁻¹	Fit to VSP onset, see Fig. S1
speed _KCNQ _PIP₂	0.05	µm² s⁻¹	Rate limiting if <0.05
KD_KCNQ _PIP₂	2,000	µm⁻²	As for PH probes
I_KCNQ^b	a * (PIP₂_KCNQ)²	pA	See Fig. 4
speed_PH_PIP₂	1	µM⁻¹ s⁻¹	Affects timing if <1
KD_PH_PIP₂	2	µM	Lemmon et al. (1995); Hirose et al. (1999); as in Xu et al. (2003); Winks et al. (2005)
speed_PH_IP₃	10	µM⁻¹ s⁻¹	To not be rate limiting, from Xu et al. (2003)
KD_PH_IP₃	0.1	µM	Hirose et al. (1999); Lemmon et al. (1995), as in Winks et al. (2005); Xu et al. (2003)
k_IP₃ase	0.08	s⁻¹	From Xu et al. (2003)

Parameter	Value	Units	Rationale
k_PLC	0.1	µm² s⁻¹	Oxo-M onset of current inhibition
k_PLConPIP	0.14 * k_PLC	µm² s⁻¹	See Horowitz et al. (2005)
k_PLCbasal	0.0025	s⁻¹	To keep resting IP₃ at 0.16 µM
k_4K	2.6 × 10⁻⁴	s⁻¹	Current recovery after Oxo-M
k_4P	0.006	s⁻¹	To keep PI(4)P levels stable at rest
k_5K	0.02	s⁻¹	Current recovery after VSP
k_5P	0.014	s⁻¹	To keep PIP₂ levels stable at rest
k_VSP^a	11.3 * f(V)	s⁻¹	Fit to VSP onset, see Fig. S1
speed _KCNQ _PIP₂	0.05	µm² s⁻¹	Rate limiting if <0.05
KD_KCNQ _PIP₂	2,000	µm⁻²	As for PH probes
I_KCNQ^b	a * (PIP₂_KCNQ)²	pA	See Fig. 4
speed_PH_PIP₂	1	µM⁻¹ s⁻¹	Affects timing if <1
KD_PH_PIP₂	2	µM	Lemmon et al. (1995); Hirose et al. (1999); as in Xu et al. (2003); Winks et al. (2005)
speed_PH_IP₃	10	µM⁻¹ s⁻¹	To not be rate limiting, from Xu et al. (2003)
KD_PH_IP₃	0.1	µM	Hirose et al. (1999); Lemmon et al. (1995), as in Winks et al. (2005); Xu et al. (2003)
k_IP₃ase	0.08	s⁻¹	From Xu et al. (2003)

Forward reactions of PIP₂ binding are speed_, and reverse reactions are speed_ * KD_; see Table S1.

f(V) = 1/(1+exp((−1.5*q_e/k_BT*(V−0.1)))) with q_e/k_BT = 25 mV.

a = channel number * open probability * single-channel current.