TI  - Type II regulatory subunit (RII) of the  cAMP-dependent protein kinase 
      interaction with  A-kinase  anchor proteins requires isoleucines 3 and 5.
PG  - 24245-51
AB  - Compartmentalization of the <prot>type II cAMP-dependent protein kinase</prot> is
      maintained by association of the regulatory subunit ( RII ) with  A-Kinase
      Anchor Proteins (AKAPs) . In previous studies (Scott, J. D., Stofko, R. E.,
      McDonald, J. R., Comer, J. D., Vitalis, E. A., and Mangili J. (1990) J.
      Biol. Chem. 265, 21561-21566) we have shown that dimerization of    <prot>RII alpha</prot>   
      was required for interaction with the cytoskeletal component
       <prot>microtubule-associated protein 2</prot>.  In this report we show that the
      localization and dimerization domains of <prot>RII alpha</prot> are contained within
      the first thirty residues of each RII protomer. <prot>RII des-5</prot> (an
      amino-terminal deletion mutant lacking residues 1-5) was unable to bind
      AKAPs but retained the ability to dimerize. <prot>RII alpha</prot> I3A,I5A (a mutant
      where isoleucines 3 and 5 were replaced with alanine) was unable to bind a
      variety of AKAPs. Mutation of both isoleucines decreased AKAP binding
      without affecting dimerization, cAMP binding, or the overall secondary
      structure of the protein. Measurement of <prot>RII alpha</prot> I3A,I5A interaction
      with the human <prot>thyroid AKAP</prot>, <prot>Ht 31</prot>, by two independent methods suggests
      that mutation of isoleucines 3 and 5 decreases affinity by at least
      6-fold. Therefore, we propose that two isoleucine side chains on each RII
      protomer are principle sites of contact with the conserved amphipathic
      helix binding domain on AKAPs.
AD  - Vollum Institute, Portland, Oregon 97201-3098.
