Crystal Structure of a PCP/Sfp Complex Reveals the Structural Basis for Carrier Protein Posttranslational Modification

Phosphopantetheine transferases represent a class of enzymes found throughout all forms of life. From a structural point of view, they are subdivided into three groups, with transferases from group II being the most widespread. They are required for the post-translational modification of carrier proteins involved in diverse metabolic pathways. We determined the crystal structure of the group II phosphopantetheine transferase Sfp from Bacillus in complex with a substrate carrier protein in the presence of coenzyme A and magnesium, and observed two protein-protein interaction sites. Mutational analysis showed that only the hydrophobic contacts between the carrier protein's second helix and the C-terminal domain of Sfp are essential for their productive interaction. Comparison with a similar structure of a complex of human proteins suggests that the mode of interaction is highly conserved in all domains of life.