An N-terminally truncated form of cyclic GMP-dependent protein kinase I? (PKG I?) is monomeric and autoinhibited and provides a model for activation.

ABSTRACT: The type I cGMP-dependent protein kinases (PKG I) serve essential physiological functions, including smooth muscle relaxation, cardiac remodeling, and platelet aggregation. These enzymes form homodimers through their N-terminal dimerization domains, a feature implicated in regulating their cooperative activation. Previous investigations into the activation mechanisms of PKG I isoforms have been largely influenced by structures of the cAMP-dependent protein kinase (PKA). Here, we examined PKG I? activation by cGMP and cAMP by engineering a monomeric form that lacks N-terminal residues 1-53 (?53). We found that the construct exists as a monomer as assessed by whole-protein MS, size-exclusion chromatography, and small-angle X-ray scattering (SAXS). Reconstruction of the SAXS 3D envelope indicates that ?53 has a similar shape to the heterodimeric RI?-C complex of PKA. Moreover, we found that the ?53 construct is autoinhibited in its cGMP-free state and can bind to and be activated by cGMP in a manner similar to full-length PKG I? as assessed by surface plasmon resonance (SPR) spectroscopy. However, we found that the ?53 variant does not exhibit cooperative activation, and its cyclic nucleotide selectivity is diminished. These findings support a model in which, despite structural similarities, PKG I? activation is distinct from that of PKA, and its cooperativity is driven by in trans interactions between protomers.

SUBMITTER: Moon TM 

PROVIDER: S-EPMC5971464 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature