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Molecule Parameter List for Sos

The statistics table lists the distribution of a molecule acting either as a substrate, product, enzyme or as a molecule within the network. The text color of a molecule is highlighted by color.

Statistics

Sos participated as	Molecule	Sum total of	Enzyme	Substrate of an enzyme	Product of an enzyme	Substrate in Reaction	Product in Reaction
No. of occurrences	1	0	0	0	0	1	1

Accession and Pathway Details

Accession Name	Accession No.	Accession Type	Pathway Link
mkp1_feedback_ effects	4	Network	Shared_Object_mkp1_feedback_effects,  Sos,  PKC,   MAPK,  PLA2,  Ras,   PDGFR
This is a network involving the MAPK-PKC feedback loop with input from the PDGFR in the synapse. The distinctive feature of this model is that it includes MKP-1 induction by MAPK, and the consequent inhibitory regulation of MAPK and the feedback loop. Lots of interesting dynamics arise from this. This link provides supplementary material for the paper Bhalla US et al. Science (2002) 297(5583):1018-23. In the form of several example simulations and demos for the figures in the paper.

Sos acting as a Molecule in  mkp1_feedback_effects Network

Name	Accession Name	Pathway Name	Initial Conc. (uM)	Volume (fL)	Buffered
Sos	mkp1_feedback_ effects Accession No. : 4	Sos Pathway No. : 33	0.1	1000	No
I have tried using low (0.02 uM) initial concs, but these give a very flat response to EGF stim although the overall activation of Ras is not too bad. I am reverting to 0.1 because we expect a sharp initial response, followed by a decline.

Sos acting as a Substrate in a reaction in  mkp1_feedback_effects Network

Kd is calculated only for second order reactions, like nA+nB <->nC or nA<->nC+nD, where n is number and A,B,C,D are molecules, where as for first order reactions Keq is calculated. Kd for higher order reaction are not consider.

Name	Accession Name	Pathway Name	Kf	Kb	Kd	tau	Reagents
Grb2_bind_Sos	mkp1_feedback_ effects Accession No. : 4	Sos Pathway No. : 33	0.025 (uM^-1 s^-1)	0.0168 (s^-1)	Kd(bf) = 0.672(uM)	-	Substrate Grb2 Sos Product Sos.Grb2
As there are 2 SH3 domains, this reaction could be 2nd order. I have a Kd of 22 uM from peptide binding (Lemmon et al JBC 269:50 pg 31653). However, Chook et al JBC 271:48 pg30472 say it is 0.4uM with purified proteins, so we believe them. They say it is 1:1 binding. Porfiri and McCormick JBC 271 also have related data. After comparing with the time-course of 1 min and the efficacy of activation of Ras, settle on Kd of 0.672 which is close to the Chook et al value.

Sos acting as a Product in a reaction in  mkp1_feedback_effects Network

Kd is calculated only for second order reactions, like nA+nB <->nC or nA<->nC+nD, where n is number and A,B,C,D are molecules, where as for first order reactions Keq is calculated. Kd for higher order reaction are not consider.

Name	Accession Name	Pathway Name	Kf	Kb	Kd	tau	Reagents
dephosph_Sos	mkp1_feedback_ effects Accession No. : 4	Sos Pathway No. : 33	0.001 (s^-1)	0 (s^-1)	-	-	Substrate Sos* Product Sos
The best clue I have to these rates is from the time courses of the EGF activation, which is around 1 to 5 min. The dephosph would be expected to be of the same order, perhaps a bit longer. Lets use 0.002 which is about 8 min. Sep 17: The transient activation curve matches better with kf = 0.001