<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated 10-March-2004 12:46:50.126577 -->
<!-- Generated by MathSBML 2.2.1-beta-17 (25-Feb-2004) -->
<sbml xmlns="http://www.sbml.org/sbml/level2"
    level="2"
    version="1">
 <model id="GProteinModel"
     name="GProteinModel">
  <listOfFunctionDefinitions>
   <functionDefinition id="stim"
       name="stim">
    <math xmlns="http://www.w3.org/1998/Math/MathML">
     <lambda>
      <bvar>
       <ci>t</ci>
      </bvar>
      <apply>
       <plus/>
       <apply>
        <ci>If</ci>
        <apply>
         <leq/>
         <apply>
          <times/>
          <cn type="integer">-1</cn>
          <cn type="rational">25<sep/>2</cn>
         </apply>
         <apply>
          <plus/>
          <ci>t</ci>
          <cn type="integer">-130</cn>
         </apply>
         <cn type="rational">25<sep/>2</cn>
        </apply>
        <cn type="integer">1</cn>
        <cn type="integer">0</cn>
       </apply>
       <apply>
        <ci>If</ci>
        <apply>
         <leq/>
         <apply>
          <times/>
          <cn type="integer">-1</cn>
          <cn type="rational">25<sep/>2</cn>
         </apply>
         <apply>
          <plus/>
          <ci>t</ci>
          <cn type="integer">-80</cn>
         </apply>
         <cn type="rational">25<sep/>2</cn>
        </apply>
        <cn type="integer">1</cn>
        <cn type="integer">0</cn>
       </apply>
       <apply>
        <ci>If</ci>
        <apply>
         <leq/>
         <apply>
          <times/>
          <cn type="integer">-1</cn>
          <cn type="rational">25<sep/>2</cn>
         </apply>
         <apply>
          <plus/>
          <ci>t</ci>
          <cn type="integer">-30</cn>
         </apply>
         <cn type="rational">25<sep/>2</cn>
        </apply>
        <cn type="integer">1</cn>
        <cn type="integer">0</cn>
       </apply>
      </apply>
     </lambda>
    </math>
   </functionDefinition>
  </listOfFunctionDefinitions>
  <listOfUnitDefinitions/>
  <listOfCompartments>
   <compartment id="Compartment1"
       name="Compartment1"/>
  </listOfCompartments>
  <listOfSpecies>
   <species id="L"
       name="L"
       compartment="Compartment1"
       boundaryCondition="true"
       constant="false"
       initialConcentration="0.01"/>
   <species id="R"
       name="R"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="1"/>
   <species id="RL"
       name="RL"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="RLalphaGDPbetagamma"
       name="RLalphaGDPbetagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="RLalphaGTPbetagamma"
       name="RLalphaGTPbetagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="RLalphabetagamma"
       name="RLalphabetagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="X"
       name="X"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="1"/>
   <species id="XalphaGTP"
       name="XalphaGTP"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="activeX"
       name="activeX"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="Y"
       name="Y"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="1"/>
   <species id="Ybetagamma"
       name="Ybetagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="activeY"
       name="activeY"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="GDP"
       name="GDP"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="10"/>
   <species id="GTP"
       name="GTP"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="10"/>
   <species id="betagamma"
       name="betagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0.1"/>
   <species id="alphaGDP"
       name="alphaGDP"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0.1"/>
   <species id="alphaGDPbetagamma"
       name="alphaGDPbetagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="alphaGTP"
       name="alphaGTP"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
   <species id="alphaGTPbetagamma"
       name="alphaGTPbetagamma"
       compartment="Compartment1"
       boundaryCondition="false"
       constant="false"
       initialConcentration="0"/>
  </listOfSpecies>
  <listOfParameters/>
  <listOfRules>
   <assignmentRule variable="L"
       metaid="rule1">
    <math xmlns="http://www.w3.org/1998/Math/MathML">
     <apply>
      <ci>stim</ci>
      <ci>t</ci>
     </apply>
    </math>
   </assignmentRule>
  </listOfRules>
  <listOfReactions>
   <reaction id="reaction1"
       name="reaction1"
       reversible="true"
       fast="false">
    <listOfReactants>
     <speciesReference species="L"/>
     <speciesReference species="R"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="RL"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <plus/>
       <apply>
        <times/>
        <ci>k1</ci>
        <ci>L</ci>
        <ci>R</ci>
       </apply>
       <apply>
        <times/>
        <cn type="integer">-1</cn>
        <apply>
         <times/>
         <ci>k2</ci>
         <ci>RL</ci>
        </apply>
       </apply>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k1"
          value="1"/>
      <parameter id="k2"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction2"
       name="reaction2"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="alphaGDPbetagamma"/>
     <speciesReference species="RL"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="RLalphaGDPbetagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>alphaGDPbetagamma</ci>
       <ci>k3</ci>
       <ci>RL</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k3"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction3"
       name="reaction3"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="RLalphaGDPbetagamma"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="GDP"/>
     <speciesReference species="RLalphabetagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>k4</ci>
       <ci>RLalphaGDPbetagamma</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k4"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction4"
       name="reaction4"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="GTP"/>
     <speciesReference species="RLalphabetagamma"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="RLalphaGTPbetagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>GTP</ci>
       <ci>k5</ci>
       <ci>RLalphabetagamma</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k5"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction5"
       name="reaction5"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="RLalphaGTPbetagamma"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="alphaGTPbetagamma"/>
     <speciesReference species="RL"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>k6</ci>
       <ci>RL</ci>
       <ci>RLalphaGTPbetagamma</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k6"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction6"
       name="reaction6"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="alphaGTPbetagamma"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="alphaGTP"/>
     <speciesReference species="betagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>alphaGTPbetagamma</ci>
       <ci>k7</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k7"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction7"
       name="reaction7"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="alphaGTP"/>
     <speciesReference species="X"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="XalphaGTP"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <plus/>
       <apply>
        <times/>
        <ci>a8</ci>
        <ci>alphaGTP</ci>
        <ci>X</ci>
       </apply>
       <apply>
        <times/>
        <cn type="integer">-1</cn>
        <apply>
         <times/>
         <ci>d8</ci>
         <ci>XalphaGTP</ci>
        </apply>
       </apply>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="a8"
          value="1"/>
      <parameter id="d8"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction8"
       name="reaction8"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="XalphaGTP"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="activeX"/>
     <speciesReference species="alphaGTP"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>k8</ci>
       <ci>XalphaGTP</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k8"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction9"
       name="reaction9"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="activeX"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="X"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>activeX</ci>
       <ci>k12</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k12"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction10"
       name="reaction10"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="betagamma"/>
     <speciesReference species="Y"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="Ybetagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <plus/>
       <apply>
        <times/>
        <ci>a9</ci>
        <ci>betagamma</ci>
        <ci>Y</ci>
       </apply>
       <apply>
        <times/>
        <cn type="integer">-1</cn>
        <apply>
         <times/>
         <ci>d9</ci>
         <ci>Ybetagamma</ci>
        </apply>
       </apply>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="a9"
          value="1"/>
      <parameter id="d9"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction11"
       name="reaction11"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="Ybetagamma"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="activeY"/>
     <speciesReference species="betagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>k9</ci>
       <ci>Ybetagamma</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k9"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction12"
       name="reaction12"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="activeY"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="Y"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>activeY</ci>
       <ci>k13</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k13"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction13"
       name="reaction13"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="alphaGTP"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="alphaGDP"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>alphaGTP</ci>
       <ci>k10</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k10"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
   <reaction id="reaction14"
       name="reaction14"
       reversible="false"
       fast="false">
    <listOfReactants>
     <speciesReference species="alphaGDP"/>
     <speciesReference species="betagamma"/>
    </listOfReactants>
    <listOfProducts>
     <speciesReference species="alphaGDPbetagamma"/>
    </listOfProducts>
    <listOfModifiers/>
    <kineticLaw timeUnits="time"
        substanceUnits="substance">
     <math xmlns="http://www.w3.org/1998/Math/MathML">
      <apply>
       <times/>
       <ci>alphaGDP</ci>
       <ci>betagamma</ci>
       <ci>k11</ci>
      </apply>
     </math>
     <listOfParameters>
      <parameter id="k11"
          value="1"/>
     </listOfParameters>
    </kineticLaw>
   </reaction>
  </listOfReactions>
  <listOfEvents/>
 </model>
</sbml>