A dynamic mechanism for AKAP binding to RII isoforms of cAMP-dependent protein kinase.
A kinase-anchoring proteins (AKAPs) target PKA to specific microdomains by using an amphipathic helix that docks to N-terminal dimerization and docking (D/D) domains of PKA regulatory (R) subunits. To understand specificity, we solved the crystal structure of the helical motif from D-AKAP2, a dual-specific AKAP, bound to the RIIalpha D/D domain. The 1.6 Angstrom structure reveals how this dynamic, hydrophobic docking site is assembled. A stable, hydrophobic docking groove is formed by the helical interface of two RIIalpha protomers. The flexible N terminus of one protomer is then recruited to the site, anchored to the peptide through two essential isoleucines. The other N terminus is disordered. This asymmetry provides greater possibilities for AKAP docking. Although there is strong discrimination against RIalpha in the N terminus of the AKAP helix, the hydrophobic groove discriminates against RIIalpha. RIalpha, with a cavity in the groove, can accept a bulky tryptophan, whereas RIIalpha requires valine.
Kinderman
Francis S
FS
Department of Chemistry and Biochemistry, University of California, San Diego, San Diego, California 92093, USA.
Kim
Choel
C
von Daake
Sventja
S
Ma
Yuliang
Y
Pham
Bao Q
BQ
Spraggon
Glen
G
Xuong
Nguyen-Huu
NH
Jennings
Patricia A
PA
Taylor
Susan S
SS
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D000242:Cyclic AMP / Q000378:metabolism; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins; D051381:Rats; D015398:Signal Transduction; D012996:Solutions; D013379:Substrate Specificity
D048868:Adaptor Proteins, Signal Transducing; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C400224:Ht 31 protein, synthetic; D007527:Isoenzymes; C517836:Prkar1a protein, rat; C517822:Prkar2a protein, rat; D011506:Proteins; D012996:Solutions; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases