Purification of recombinant DHHC proteins using an insect cell expression system

Abstract

DHHC enzymes are a family of integral membrane proteins that catalyze the posttranslational addition of palmitate, a 16-carbon fatty acid, onto a cysteine residue of a protein. While the library of identified palmitoylated proteins has grown tremendously over the years, biochemical and mechanistic studies on DHHC proteins are challenged by the innate difficulty of purifying the enzyme in large amounts. Here we describe our protocol for preparing recombinant DHHC proteins tagged with a hexahistidine sequence and a FLAG epitope that aid in the purification. This procedure has been tested successfully in purifying several members of the enzyme family; DHHC3 and its catalytically inactive cysteine mutant, DHHS3 are used as examples. The recombinant protein is extracted from whole cell lysates using the detergent dodecylmaltoside (DDM) and is subjected to a two-column purification. Homogeneity and monodispersity of the purified protein are checked by size exclusion chromatography (SEC). A preparation from a 400-mL infection of Sf9 insect cell culture typically yields 0.5 mg of DHHC3 and 1.0 mg of catalytically inactive DHHS3. Both forms appear monodisperse up to a concentration of 1 mg/mL by SEC.