Partially folded bovine pancreatic trypsin inhibitor analogues attain fully native structures when co-crystallized with S195A rat trypsin.
Level 5 - mechanism / opinion, no new human data
In vitro structural biology bench study without human data
PubMed 18054043 · doi:10.1016/j.jmb.2007.10.084
What was done
Crystal structures were determined at 1.7 Å resolution for complexes between an inactive rat trypsin mutant (S195A) and two chemically synthesized, partially folded bovine pancreatic trypsin inhibitor (BPTI) analogues: [14-38](Abu) (retaining only the Cys14–Cys38 disulfide bond with four cysteines replaced by alpha-amino-n-butyric acid) and K26P,A27D[14-38](Abu) (incorporating two additional beta-turn substitutions). The complex of S195A trypsin with wild-type BPTI was solved as a control.
What was found
At 1.7 Å resolution, the tertiary folds of both partially folded BPTI analogues bound to S195A trypsin in the crystal lattice were essentially superimposable on wild-type BPTI, despite marked differences in their degree of folding previously detected in solution by biophysical methods. Specific coordinate root-mean-square deviations and binding parameters were not reported in the abstract.
Why it matters
These results demonstrate that interaction with a physiological binding partner can template and stabilize a fully native-like tertiary fold in protein variants that are largely unstructured in solution.
Limits
The study is restricted to in vitro crystalline states of an engineered mutant enzyme complex, which may not represent conformational dynamics or intermediate states in solution. Numerical structural alignment metrics and solution thermodynamic data were omitted from the abstract.
Cited by
- supports Replacing the active site serine's hydroxyl oxygen with a hydrogen turns the residue into alanine and renders a serine protease completely functionless without altering its 3D structure.