Figure 6.

Phosphorylation by SNAK promotes SNAP-23 assembly with syntaxin. (A) HeLa cells expressing SNAP-23 and syntaxin 4 in the absence or presence of SNAK were labeled with [³⁵S]methionine for 15 min and chased in complete medium. After incubation for various times at 37°C, the cells were harvested, lysed in Triton X-100, immunoprecipitated with the use of control (C) or anti-syntaxin 4 serum, and analyzed by SDS-PAGE and fluorography. (B) The relative amount of [³⁵S]SNAP-23 coprecipitated with the syntaxin 4 serum at different times of chase in the absence (□) or in the presence (▪) of SNAK was determined by phosphorimager analysis. The amount of [³⁵S]SNAP-23 present is expressed in arbitrary phosphorimager units (AU). Each value represents the results from two independent experiments with SD.