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Molecule Parameter List for Raf*-GTP-Ras

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

Raf*-GTP-Ras 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	2	0	0	0	1

Accession and Pathway Details

Accession Name	Accession No.	Accession Type	Pathway Link
MAPK-bistability -fig1c	35	Network	Shared_Object_MAPK-bistability-fig1c,  Sos,  PKC,   MAPK,  PLA2,  Ras,   PDGFR
Model for figure 1c in Bhalla US et al. Science (2002) 297(5583):1018-23. The demo for this figure is available here. This synaptic signaling model is without the MKP-1 feedback, so it is bistable and remains so over long periods.

Raf*-GTP-Ras acting as a Molecule in  MAPK-bistability-fig1c Network

Name	Accession Name	Pathway Name	Initial Conc. (uM)	Volume (fL)	Buffered
Raf*-GTP-Ras	MAPK-bistability -fig1c Accession No. : 35	MAPK Pathway No. : 182	0	1000	No
This is the main activated form of craf. It requires binding to ras for activation, but the presence of the phosphorylation increases this binding. See Leevers 1994 Nature 369:411-414 and Hallberg et al 1994 JBC 269(6):3913-3916

Raf*-GTP-Ras acting as an Enzyme in  MAPK-bistability-fig1c Network

	Enzyme Molecule / Enzyme Activity	Accession Name	Pathway Name	Km (uM)	kcat (s^-1)	Ratio	Enzyme Type	Reagents
1	Raf*-GTP-Ras / Raf*-GTP-Ras.1	MAPK-bistability -fig1c Accession No. : 35	MAPK Pathway No. : 182	0.159091	0.105	4	explicit E-S complex	Substrate MAPKK Product MAPKK-ser
	Kinetics are the same as for the craf-1* activity, ie., k1=1.1e-6, k2=.42, k3 =0.105 These are based on Force et al PNAS USA 91 1270-1274 1994. They report Km for MAPKK of 0.8 uM. and a Vmax of ~500 fm/min/ug. These parms cannot reach the observed 4X stimulation of MAPK. So we increase the affinity, ie, raise k1 5x to 5.5e-6 which is equivalent to 5-fold reduction in Km to about 0.16. This is, of course, dependent on the amount of MAPKK present.
2	Raf*-GTP-Ras / Raf*-GTP-Ras.2	MAPK-bistability -fig1c Accession No. : 35	MAPK Pathway No. : 182	0.159091	0.105	4	explicit E-S complex	Substrate MAPKK-ser Product MAPKK*
	Same kinetics as other c-raf activated forms. See Force et al PNAS 91 1270-1274 1994.

Raf*-GTP-Ras acting as a Product in a reaction in  MAPK-bistability-fig1c 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
Ras-act-craf	MAPK-bistability -fig1c Accession No. : 35	Shared_Object_ MAPK-bistability -fig1c Pathway No. : 179	60 (uM^-1 s^-1)	0.5 (s^-1)	Kd(bf) = 0.0083(uM)	-	Substrate GTP-Ras craf-1* Product Raf*-GTP-Ras
Assume binding is fast and limited only by available Ras*. So kf = kb/[craf-1] If kb is 1/sec, then kf = 1/0.2 uM = 1/(0.2 * 6e5) = 8.3e-6 Later: Raise it by 10 X to about 1e-4, giving a Kf of 60 for Kb of 0.5 and a tau of approx 2 sec. Based on: Hallberg et al JBC 269:6 3913-3916 1994, 3% of cellular Raf is complexed with Ras. This step needed to memb-anchor and activate Raf: Leevers et al Nature 369 411-414. Also see Koide et al 1993 PNAS USA 90(18):8683-8686