This process is probably much more complicated and involves CaM. However, as I can\'t find detailed info I am bundling this into a single step. Based on Steemer and Klee pg 6863, the Kact is 0.5 uM. kf/kb = 1/(0.5 * 6e5)^2 = 1.11e-11
The rates here are so slow I do not know if we should even bother with this enz reacn. These numbers are from Liu and Storm. Other refs suggest that the Km stays the same but the Vmax goes to 10% of the CaM stim levels. Prev: k1=2.2e-9, k2 = 0.0052, k3 = 0.0013 New : k1=5.7e-8, k2=.136, k3=.034
See Hanson and Schulman again, for afterburst rates of phosph.
K inhib = 1nM from Cohen Ann Rev Bioch 1989, 4 nM from Foukes et al Assume 2 nM. kf /kb = 8.333e-4
Let us assume that the equil in this case is very far over to the right. This is probably safe.
going on the experience with CaM, we put the fast (high affinity) sites first. We only know (Stemmer and Klee) that the affinity is < 70 nM. Assuming 10 nM at first, we get kf = 2.78e-8, kb = 1. Try 20 nM. kf = 7e-9, kb = 1
K3 = 21.5, K4 = 2.8. Assuming that the K4 step happens first, we get kb/kf = 2.8 uM = 1.68e6 so kf =6e-6 assuming kb = 10
Rates set by the translocation experiments of Shen and Meyer, Science 1999.
PP2A does most of the dephosph of I1 at basal Ca levels. See the review by Cohen in Ann Rev Biochem 1989. For now, lets halve Km. k1 was 3.3e-6, now 6.6e-6
Use K3 = 21.5 uM here from Stemmer and Klee table 3. kb/kf =21.5 * 6e5 so kf = 7.75e-7, kb = 10
#s from Bramson et al CRC crit rev Biochem 15:2 93-124. They have a huge list of peptide substrates and I have chosen high-ish rates. These consts give too much PKA activity, so lower Vmax 1/3. Now, k1 = 3e-5, k2 = 36, k3 = 9 (still pretty fast). Also lower Km 1/3 so k1 = 1e-5 Cohen et al FEBS Lett 76:182-86 1977 say rate =30% PKA act on phosphokinase beta.
Lets use the fast rate consts here. Since the rates are so different, I am not sure whether the order is relevant. These correspond to the TR2C fragment. We use the Martin et al rates here, plus the Drabicowski binding consts. All are scaled by 3X to cell temp. kf = 2e-10 kb = 72 Stemmer & Klee: K1=.9, K2=1.1. Assume 1.0uM for both. kb/kf=3.6e11. If kb=72, kf = 2e-10 (Exactly the same !)....
This is tricky. There is some cooperativity here arising from interactions between the subunits of the CAMKII holoenzyme. However, the stoichiometry is 1. Kb/Kf = 6e4 #/cell. Rate is fast (see Hanson et al Neuron 12 943-956 1994) so lets say kb = 10. This gives kf = 1.6667e-4 H&S AnnRev Biochem 92 give tau for dissoc as 0.2 sec at low Ca, 0.4 at high. Low Ca = 100 nM = physiol.
Same values as for the main compartment Can the main compartment pool of Ca/CaM be used?
Diffusional equilibrium between PSD- and cytosolic compartment. According to D. Bary in Cell Movements 2nd ed 2001 D for proteins is 5e-7 cm^2/s giving 10 ms for a translocation of 1 um.
This is the model of CaMKII bistability, model 3. It exhibits bistability in CaMKII activation due to autophosphorylation at the PSD and local saturation of PP1. This version of model 3 does not include the full PKA regulatory pathway, and instead has a predefined initial amount of active PKA. This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information. In summary, you are entitled to use this encoded model in absolutely any manner you deem suitable, verbatim, or with modification, alone or embedded it in a larger context, redistribute it, commercially or not, in a restricted way or not.. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.
Affinity is up 1000X. Time to release is about 20 sec, so the kb is OK at 0.1 This makes Kf around 1.6666e-3
Rates to match curve in fig2 from Shen and Meyer, Science 284:162-166(1999), calculated for 6:1 alpha:beta CaMKII heterodimers
Rates from autocamtide phosphorylation, from Hanson and Schulman JBC 267:24 17216-17224 1992. Jan 1 1998: Speed up 12x to match fig 5.