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Molecule Parameter List for 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
GTP-Ras participated asMoleculeSum total ofEnzymeSubstrate of an enzymeProduct of an enzymeSubstrate in ReactionProduct in Reaction
No. of occurrences1001120

Accession and Pathway Details
Accession NameAccession No.Accession TypePathway Link
3d_fold_model8Network
Shared_Object_3d_fold_model PKC MAPK 
PLA2 Ras 
This model is an annotated version of the synaptic signaling network.
The primary reference is Bhalla US and Iyengar R. Science (1999) 283(5400):381-7 but several of the model pathways have been updated Bhalla US, Ram PT, Iyengar R. Science. 2002 Aug 9;297(5583):1018-23.

GTP-Ras acting as a Molecule in  
3d_fold_model Network
NameAccession NamePathway NameInitial Conc.
(uM)
Volume
(fL)
Buffered
GTP-Ras3d_fold_model
Accession No. : 8
Ras
Pathway No. : 58
01000No
Only a very small fraction (7% unstim, 15% stim) of ras is GTP-bound. Gibbs et al JBC 265(33) 20437

GTP-Ras acting as a Substrate for an Enzyme in  
3d_fold_model Network
Enzyme Molecule /
Enzyme Activity
Accession NamePathway NameKm (uM)kcat (s^-1)RatioEnzyme TypeReagents
GAP  /
GAP-inact-ras
3d_fold_model
Accession No. : 8
Ras
Pathway No. : 58
1.010410100explicit E-S complexSubstrate
GTP-Ras

Product
GDP-Ras
From Eccleston et al JBC 268(36)pp27012-19 get Kd < 2uM, kcat - 10/sec From Martin et al Cell 63 843-849 1990 get Kd ~ 250 nM, kcat = 20/min I will go with the Eccleston figures as there are good error bars (10%). In general the values are reasonably close. k1 = 1.666e-3/sec, k2 = 1000/sec, k3 = 10/sec (note k3 is rate-limiting)

GTP-Ras acting as a Product of an Enzyme in  
3d_fold_model Network
Enzyme Molecule /
Enzyme Activity
Accession NamePathway NameKm (uM)kcat (s^-1)RatioEnzyme TypeReagents
GEF*  /
GEF*-act-ras
3d_fold_model
Accession No. : 8
Ras
Pathway No. : 58
0.5050510.024explicit E-S complexSubstrate
GDP-Ras

Product
GTP-Ras
Kinetics same as GEF-bg-act-ras

GTP-Ras acting as a Substrate in a reaction in  
3d_fold_model 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.
 NameAccession NamePathway NameKfKbKdtauReagents
1Ras-act-craf3d_fold_model
Accession No. : 8
  • Shared_Object_
    3d_fold_model

    Pathway No. : 54
  • 24
    (uM^-1 s^-1)
    0.5
    (s^-1)
    Kd(bf) = 0.0208(uM)-Substrate
    GTP-Ras
    craf-1*

    Product
    Raf-GTP-Ras*
      Assume the binding is fast and is limited only by the amount of Ras* available. 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 4e-5 From Hallberg et al JBC 269:6 3913-3916 1994, 3% of cellular Raf is complexed with Ras. So we raise kb 4 x to 4 This step needed to memb-anchor and activate Raf: Leevers et al Nature 369 411-414
    2
  • Ras-intrinsic-GT
    Pase
  • 3d_fold_model
    Accession No. : 8
    Ras
    Pathway No. : 58
    0.0001
    (s^-1)
    0
    (s^-1)
    --Substrate
    GTP-Ras

    Product
    GDP-Ras
      This is extremely slow (1e-4), but it is significant as so little GAP actually gets complexed with it that the total GTP turnover rises only by 2-3 X (see Gibbs et al, JBC 265(33) 20437-20422) and Eccleston et al JBC 268(36) 27012-27019 kf = 1e-4



    Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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