title: Zinc binding drives sheet formation by the SAM domain of diacylglycerol kinase δ.
abstract: The diacylglycerol kinase (DGK) family of enzymes plays critical roles in lipid signaling pathways by converting diacylglycerol to phosphatidic acid, thereby downregulating signaling by the former and upregulating signaling by the latter second messenger. Ten DGK family isozymes have been identified to date, which possess different interaction motifs imparting distinct temporal and spatial control of DGK activity to each isozyme. Two DGK family members, δ and η, contain a sterile alpha motif (SAM) domain. The SAM domain of DGKδ1 forms helical polymers that are important for retaining the enzyme in cytoplasmic puncta, thereby inhibiting activity at the plasma membrane until pathway activation. Because zinc was found to be important for stabilizing the similar SAM polymers of the scaffolding protein Shank-3, we investigated the potential role of zinc in DGKδ SAM domain (DGKδSAM) assembly. We find that DGKδSAM binds zinc at multiple sites, driving the organization of the DGKδSAM into large sheets of polymers. Moreover, a mutant DGKδ containing a SAM domain refractory to zinc binding diminishes the formation of cytoplasmic puncta, shows partially impaired regulation of transport to the plasma membrane, and lacks the ability to inhibit the formation of CopII coated vesicles. These results suggest that zinc may play an important role in the assembly and physiology of the DGKδ isozyme.
authors.affiliation: Department of Chemistry and Biochemistry, Institute of Genomics and Proteomics, University of California, Los Angeles, CA 90095-1570, USA.
authors.forename: Mary Jane
authors.initials: MJ
authors.lastname: Knight
authors.forename: Marisa K
authors.initials: MK
authors.lastname: Joubert
authors.forename: Megan L
authors.initials: ML
authors.lastname: Plotkowski
authors.forename: Janette
authors.initials: J
authors.lastname: Kropat
authors.forename: Mari
authors.initials: M
authors.lastname: Gingery
authors.forename: Fumio
authors.initials: F
authors.lastname: Sakane
authors.forename: Sabeeha S
authors.initials: SS
authors.lastname: Merchant
authors.forename: James U
authors.initials: JU
authors.lastname: Bowie
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D019852:Diacylglycerol Kinase / Q000032:analysis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004075:Diglycerides / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D058105:Polymerization; D017434:Protein Structure, Tertiary; D015032:Zinc / Q000378:metabolism*
chemical_list: D004075:Diglycerides; C497139:DGKD protein, human; D019852:Diacylglycerol Kinase; D015032:Zinc