title: A flagellar A-kinase anchoring protein with two amphipathic helices forms a structural scaffold in the radial spoke complex.
abstract: A-kinase anchoring proteins (AKAPs) contain an amphipathic helix (AH) that binds the dimerization and docking (D/D) domain, RIIa, in cAMP-dependent protein kinase A (PKA). Many AKAPs were discovered solely based on the AH-RIIa interaction in vitro. An RIIa or a similar Dpy-30 domain is also present in numerous diverged molecules that are implicated in critical processes as diverse as flagellar beating, membrane trafficking, histone methylation, and stem cell differentiation, yet these molecules remain poorly characterized. Here we demonstrate that an AKAP, RSP3, forms a dimeric structural scaffold in the flagellar radial spoke complex, anchoring through two distinct AHs, the RIIa and Dpy-30 domains, in four non-PKA spoke proteins involved in the assembly and modulation of the complex. Interestingly, one AH can bind both RIIa and Dpy-30 domains in vitro. Thus, AHs and D/D domains constitute a versatile yet potentially promiscuous system for localizing various effector mechanisms. These results greatly expand the current concept about anchoring mechanisms and AKAPs.
authors.affiliation: Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Sivadas
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Dienes
authors.forename: Martin
authors.initials: M
authors.lastname: St Maurice
authors.forename: William D
authors.initials: WD
authors.lastname: Meek
authors.forename: Pinfen
authors.initials: P
authors.lastname: Yang
mesh_terms: D054758:A Kinase Anchor Proteins / Q000737:chemistry* / Q000378:metabolism*; D002478:Cells, Cultured; D016825:Chlamydomonas reinhardtii / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D005407:Flagella / Q000201:enzymology* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D016296:Mutagenesis; D010940:Plant Proteins; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D054758:A Kinase Anchor Proteins; D010940:Plant Proteins; D015800:Protozoan Proteins; C060324:radial spoke protein, Chlamydomonas