The daily cycle of melatonin biosynthesis in mammals is regulated by arylalkylamine N-acetyltransferase (EC 184.108.40.206, AANAT), making it an attractive target for therapeutic control of abnormal melatonin production in mood and sleep disorders. Drosophila melanogaster dopamine N-acetyltransferase (Dat) is an AANAT. Until this report, no insect Dat structure had been solved, and consequently, the structural basis for its acetyl-transfer activity was not well understood. We report herein the high-resolution crystal structure for a D. melanogaster Dat/acetyl coenzyme A (AcCoA) complex obtained using one-edge (Selenium) single-wavelength anomalous diffraction. The binding study by isothermal titration calorimetry suggested that the cofactor bound to Dat first before substrate. Examination of the complex structure and a substrate-docked model indicated that Dat contains a novel AANAT catalytic triad. A site-directed mutagenesis, a kinetic study and pH-rate profiles confirmed that Glu47, Ser182, and Ser186 were critical for catalysis. Collectively, our results suggest that Dat possesses a specialized active site structure dedicated to a catalytic mechanism.
Epigenetic silencing of gene expression is important in cancer. Aberrant DNA CpG island hypermethylation and histone modifications are involved in the aberrant silencing of tumour-suppressor genes. LSD1 (lysine-specific demethylase 1) is a H3K4 (histone H3 Lys4) demethylase associated with ... more
Distinct spatiotemporal Ca2+ signalling events regulate fundamental aspects of eukaryotic cell physiology. Complex Ca2+ signals can be driven by release of Ca2+ from intracellular organelles that sequester Ca2+ such as the ER (endoplasmic reticulum) or through the opening of Ca2+-permeable ... more
Genetically modified mice mimicking ODDD (oculodentodigital dysplasia), a disease characterized by reduced Cx43 (connexin 43)-mediated gap junctional intercellular communication, represent an in vivo model to assess the role of Cx43 in mammary gland development and function. We previously ... more