G PROTEIN ACTIVATED STIMULATORY ALPHA SUBUNIT

Both the dopaminergic (dopamine is abbreviated 'DA' and is
indicated to bind to its receptor by an arrow) and the
andrenergic (specific for epinephrine (Epi) or norepinephrine (NE)
receptors interact with the Gs protein second messenger system.
The 's' in 'Gs' stands for 'stimulatory. The Gs complex consists
of three subunits, alpha, eta, and gamma. When all three subunits
are associated, no enzymatic activity is realized. The beta-gamma
complex has less importtant actions, while the lone alpha
subunit is believed to stimulate adenylyl cyclase. In the cartoon, I
have depicted an inactive Gs protein diffusing to the left of
the adrenergic receptor (AR), the beta-gamma subunit structure near
and to the right of AR, and an alpha-s subunit associated with the
dopaminergic receptor (DA-R). This is meant to represent the fact
that both types of receptors cause a stimulation of adenylyl cyclase.
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