Activity-guided engineering of natural product carrier proteins.

A panel of chimeric carrier proteins was developed and screened for functional activity with essential enzymes involved in carrier protein-mediated biosynthesis. Regions on either side of the recognition helix II within three carrier proteins (CPs) from distinct biosynthetic pathways were swapped in all combinations to generate 24 mutated CPs. This panel of chimeric carrier proteins was tested using two previously established and one novel carrier protein assays. The results suggest a significant contribution from multiple structural units within carrier protein structure, rather than universal recognition helix, is necessary for proper recognition and activity with partner enzymes.