*cAMP-dependent kinase

Dan Jacobson danj at WELCHGATE.WELCH.JHU.EDU
Sat Mar 14 14:36:06 EST 1992

>Does anyone have any idea of the function of the alpha subunit of the camp
>dependent kinase? ANY input would be appreciated.

Well, cAMP-dependent kinase is composed of two subunits a regulatory
subunit and a catalytic sunbunit.  In its inactive form the regulatory
subunit is bound to the the catalytic subunit and prevents it from
binding to the substrate sites on other proteins.  The regulatory
subunit has a "pseudo-substrate" region which mimmicks the sequence
of phosphorylation sites except that it lacks a Serine or Threonine 
and thus can not be phosphorylated.  The protein kinase is activated
when cAMP is present - the cAMP binds to the regulatory subunit,
inducing a conformational change which causes the regulatory subunit
to dissociate from the catalytic subunit.  The catalytic subunit is 
then free to bind target proteins and phosphorylate them.  I have 
always seen the two subunits referred to as "regulatory" and "catalytic"
(or R and C) so I'm not sure which you are calling the "alpha" subunit
- I hope the above information is enough to answer your question. 

The x-ray crystal structure of c-AMP dependent kinase was published
last July by Susan Taylor's lab in Science, 253, 407-420.


Dan Jacobson

danj at welchgate.welch.jhu.edu

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