Beyond PKA: Evolutionary and structural insights that define a docking and dimerization domain superfamily

Area of Science:

• Molecular Biology
• Structural Biology
• Evolutionary Biology

Background:

• Protein-interaction domains are crucial for forming macromolecular complexes and driving evolutionary innovation.
• The docking and dimerization (D/D) domain of the PKA regulatory subunit is identified as an ancient and conserved protein fold.
• This domain typically interacts with A-kinase-anchoring proteins (AKAPs) for cell-signaling enzyme compartmentalization.

Purpose of the Study:

• To investigate the evolutionary history and structural features of the D/D domain superfamily.
• To characterize the D/D domain of sperm autoantigenic protein 17 (SPA17) and its interactions.
• To elucidate the role of D/D domains in maintaining macromolecular architectures within organelles.

Main Methods:

• Bioinformatic and phylogenetic analyses were employed to study the D/D domain superfamily.
• Structural approaches, including crystal structure determination of SPA17 D/D domain, were utilized.
• In silico analyses, homology searching, and quantitative binding assays were performed.

Main Results:

• The D/D domain superfamily comprises 18 members with diverse functions.
• SPA17, a type II D/D domain protein, forms homodimers and tetramers and interacts with AKAP18.
• SPA17 exhibits nanomolar affinity for AKAP18 upon heterodimerization with a ropporin-1-like D/D protein.

Conclusions:

• The D/D fold is a versatile protein-interaction element with a broad range of functions.
• This domain is essential for maintaining the integrity of macromolecular architectures, such as those found in motile cilia.
• The findings expand the understanding of D/D domain roles in cellular organization and signaling.