Crystal structure of AphA class B acid phosphatase/phosphotransferase from E. coli

The crystal structure of the AphA aspecific acid phosphatase from the perip!asm of E. coli has been determined at 2.2 A resolution by MAD measurements on a NaBr derivative. The resolution of the structure has been extended to 1.4 A on a AuCl3 derivative. The quatermary structure of the active enzyme consists of a homotetramer built by using the first 23 N-terminal residues which intertwine the monomers in a stable holoenzime using only a relatively minimal interaction surface The homotetramer is the stable form present in solution. The N-terminal forms a hook which represents a new structural motif used to build a stable, although flexible multimeric enzyme. The active site ofthe native enzyme as prepared hosts a magnesium ion which can be raplaced by other metal ions. The structure explains the aspecific behaviour of AphA towards substrates