Biochemistry Question!!! 1. (8 points) In studies trying to understand the regul
ID: 60087 • Letter: B
Question
Biochemistry Question!!!
1. (8 points) In studies trying to understand the regulation of hormone-sensitive adenylate cyclase, it was discovered that non-hydrolyzable GTP analogs and cholera toxin (that inhibits the GTPase activity of Gs) were able to activate the enzyme in a sustained (irreversible) profile, therefore indicating that GTP hydrolysis represents a deactivation (turn-off) regulatory step.
a) Will these analogs or toxin have any effect on adenylate cyclase activity in the absence of any added hormone?
b) If you add an factor that increases the rate of GTPase hydrolysis of the Gs protein, will this activate or inhibit the observed downstream effect upon addition of the hormone (this is in the absence of GTP analogs or toxin). Explain your answer.
Explanation / Answer
a. Guanine nucleotide requires the interaction between the CN bond and components followed by the isomerization of the complex form an inactive one that has capacity to cyclise the ATP to c AMP .Full activation by the nucleotides can be obtained in the absence of the hormones ,activation of the guanine nuclotides is often slow and time dependency abolished by the hormone . there is likely to exist enzymatic activity associated with N which inactivates the system that convert N Gtp to N GDp which maintain sthe constant turnover in the presence of the GTP
b. There are GTP ase activating proteins are a family of the regulatory proteins whose members are activated by the G proteins and stimulate their GTP ase activity .GAP also known as RGS protein, they play avery important role in the variety of the regulatory cellular process .Large G proteins are involved in the hormone signalling and small G proteins are involved in the cellular trafficking and cell cycling .Guanine exchange factor activates the monomeric GTP ases by stimulating the release of the GDP to allow binding of the guanine triphosphate .these small GTpases act as molecular switches in the intracellular signal
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