COUPLING BACKBONE FLEXIBILITY AND AMINO-ACID-SEQUENCE SELECTION IN PROTEIN DESIGN

Using a protein design algorithm that considers side-chain packing qua ntitatively, the effect of explicit backbone motion on the selection o f amino acids in protein design was assessed in the core of the strept ococcal protein G beta 1 domain (G beta 1). Concerted backbone motion was introduced by varying G beta 1's supersecondary structure paramete r values. The stability and structural flexibility of seven of the red esigned proteins were determined experimentally and showed that core v ariants containing as many as 6 of 10 possible mutations retain native -like properties. This result demonstrates that backbone flexibility c an be combined explicitly with amino acid side-chain selection and tha t the selection algorithm is sufficiently robust to tolerate perturbat ions as large as 15% of G beta 1's native supersecondary structure par ameter values.