1Listen to the audio lecture while viewing these slides1Psychology 372Physiological PsychologySteven E. Meier, Ph.D.G-Protein ReceptorsGuanine Nucleotide-Binding Proteins2Psyc 372 – Physiological PsychologyBackground• Consist of three subunits•Alpha•Beta•Gama3Psyc 372 – Physiological PsychologyAlpha• Is loosely associated with the membrane• Is usually the coupling agent between receptors and primary effectorenzymes.• Have more than 12 types• Each has different action and name.4Psyc 372 – Physiological PsychologyFamily Group Contains• Alpha and Beta adrenergic receptors• Muscarinic Ach receptors• GABAb Receptors• Certain Glutamate receptors• Certain Serotonin Receptors• Neuropeptide Receptors• Odorant Receptors• Rhodopsin •Others5Psyc 372 – Physiological PsychologyBeta-Gamma Complex• Is more tightly fixed to the membrane • Can also affect ion channels directly.6Psyc 372 – Physiological PsychologyOther Important Structures27Psyc 372 – Physiological PsychologyAdenylyl Cyclase (AC)• Is activated by the Alpha subunit• When activated makes cAMP from ATP•cAMPis an intrace llu lar messengerATPcAMPAlpha BindingSite8Psyc 372 – Physiological PsychologyProtein Kinases• Have four subunits•Two Regulatory Subunits• Where cAMP binds• Two Catalytic Subunits•Puts phosphate groups on ion channels• Is the working part of the enzymecAMP R RCC9Psyc 372 – Physiological PsychologyExternal SignalFirst Messenger (NT)Transducer Primary EffectorReceptorSecond MessengerSecondary Effector10Psyc 372 – Physiological PsychologyG Proteins At RestX X X X X X X X X X X X X X X X X GTP Binding SiteGTP is converted to GDPGDP occupies the binding site when the receptor is at rest.ααααββββRECEPTOR BINDING SITEGDP11Psyc 372 – Physiological PsychologyWhat Happens• Stimulation• NT causes a conformational change and knocks off GDP• Result - Leaves Alpha binding site open12Psyc 372 – Physiological PsychologyStimulation beginsX X X X X X X X X X X X X X X X X GDPLeavesααααββββNT313Psyc 372 – Physiological PsychologyOpen Binding SiteX X X X X X X X X X X X X X X X X Open binding siteααααββββNT14Psyc 372 – Physiological PsychologyGTP binds to the open binding siteX X X X X XααααββββNTGTP15Psyc 372 – Physiological PsychologyConformation Change• Causes a conformational change • Get DissociationX X X X X XααααββββGTPααααNT16Psyc 372 – Physiological PsychologyAdenylyl Cyclase (AC)• Is activated by the Alpha subunit• When activated makes cAMP from ATP•cAMPis an intrace llu lar messengerATPcAMPAlpha BindingSite17Psyc 372 – Physiological PsychologyNote•αs binds on AC• When it binds, it becomes GTPase• GTPase’s convert GTP to GDP• When converts to GDP, it breaks the bond from AC• Then, rebinds with the beta subunits• At same time, NT is being removed from the receptor binding site.• Alpha and Beta’s then link to the receptor site• Repeat the process18Psyc 372 – Physiological PsychologyKinases• Kinases put phosphate groups on something.• Where: A protein (Ion Channel)• Result: Protein Kinase•Many types of PK• CAMP Protein Kinase• CaCal Protein Kinase•Protein Kinase C•Others419Psyc 372 – Physiological PsychologyProtein Kinases• Has four subunits•Two Regulatory Subunits•Where enzymes (cAMP) binds• Two Catalytic Subunits•Puts phosphate groups on ion channels• Is the working part of the enzymecAMP R
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