• backbone degrees of freedom;
  • protein design;
  • protein G;
  • supersecondary structure parameters


Using a protein design algorithm that considers side-chain packing quantitatively, the effect of explicit backbone motion on the selection of amino acids in protein design was assessed in the core of the streptococcal protein G β1 domain (Gβ1). Concerted backbone motion was introduced by varying Gβ1′s supersecondary structure parameter values. The stability and structural flexibility of seven of the redesigned proteins were determined experimentally and showed that core variants containing as many as 6 of 10 possible mutations retain native-like properties. This result demonstrates that backbone flexibility can be combined explicitly with amino acid side-chain selection and that the selection algorithm is sufficiently robust to tolerate perturbations as large as 15% of Gβ1's native supersecondary structure parameter values.