Publications
Abstract
Human lipin1 catalyzes the highly regulated conversion of phosphatidic acids to diacylglycerides. Lipin's cellular location, protein partners, and biological function are directed by phosphorylation-dephosphorylation events catalyzed by the phosphoserine phosphatase dullard. To define the determinants of dullard substrate recognition and catalysis, and hence, lipin regulation, steady-state kinetic analysis was performed on phosphoserine-bearing nonapeptides based on the phosphorylation sites of lipin. The results demonstrate that dullard shows specificity for the peptide corresponding to the insulin-dependent phosphorylation site (Ser106) of lipin with a k(cat)/K(m) of 2.9 × 10(4) M(-1) s(-1). These results are consistent with a coil-loop structure for the insulin-dependent phosphorylation site on human lipin1 and make unlikely the requirement for an adaptor protein to confer activity such as that proposed for the yeast homologue.
Figure 1. Schematic diagram of human lipin1 with domains delimited. Sites of serine phosphorylation selected for peptide screening are marked.
Figure 2. Ribbon diagrams of the homology model of dullard (left) and X-ray crystal structures of Mg(II)-dependent phosphatase 1 (center) and the phosphatase domain of polynucleotide kinase/phosphatase (right). The conserved Rossmann fold of the HADSF is colored blue, and inserted segments are colored yellow, with the catalytic nucleophile colored red to mark the active site.
Figure 3. Dullard model (red, stringently conserved) shown as a coil (left) and in space-filling representation (center and right) with peptide (cyan sticks) from Scp1 overlaid (right) by superimposing the Scp1 9-mer peptide complex structure (PDB entry 2GHQ) onto the dullard model and removing the Scp1 protein.
2011 HAD Superfamily Publication
Reprinted with permission from Biochemistry.
© 2011 American Chemical Society.
