An Isoform-Specific Myristylation Switch Targets Type II PKA Holoenzymes to Membranes.

protein kinase is regulated in part by N-terminal myristylation of its catalytic (C) subunit. Structural information about the role of myristylation in membrane targeting of has been limited. In mammalian cells there are four functionally non-redundant duanyu1529 regulatory subunits (RIα, RIβ, RIIα, and RIIβ). duanyu1529 is assembled as an inactive R2C2 holoenzyme in cells. To explore the role of N-myristylation in membrane targeting of duanyu1529 holoenzymes, we solved crystal structures of RIα:myrC and RIIβ2:myrC2, and showed that the N-terminal myristylation site in the myrC serves as a flexible "switch" that can potentially be mobilized for membrane anchoring of RII, but not RI, holoenzymes. Furthermore, we synthesized nanodiscs and showed by electron microscopy that membrane targeting through the myristic acid is specific for the RII holoenzyme. This membrane-anchoring myristylation switch is independent of A Kinase Anchoring Proteins (AKAPs) that target duanyu1529 to membranes by other mechanisms.

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