期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 107, 期 7, 页码 2824-2829出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0907668107
关键词
mutually exclusive folding; design; HIV protease; molecular switch; barnase
资金
- National Institutes of Health [GM069755]
Alternate frame folding (AFF) is a novel mechanism by which allostery can be introduced into a protein where none may have existed previously. We employ this technology to convert the cytotoxic ribonuclease barnase into an artificial zymogen that is activated by HIV-1 protease. The AFF modification entails partial duplication of the polypeptide chain and mutation of a key catalytic residue in one of the duplicated segments. The resulting molecule can fold in one of two frames to yield the wild-type structure or a circularly permuted form in which the positions of the N- and C-termini are exchanged with a surface loop. It cannot take on both structures simultaneously because each competes for a shared amino acid sequence. An HIV-1 protease recognition sequence is inserted into one of the surface loops in the nonpermuted frame, and cleavage induces a shift from the nonpermuted fold to the permuted fold. Using the AFF mechanism, we were able to suppress k(cat)/K-M by 250-fold in the proenzyme relative to wild-type barnase. HIV-1 protease cleavage subsequently increases k(cat)/K-M by 130-fold. AFF is significant because it is general and can in principle be used to control activity of many enzymes, including those whose functions are not regulated by any existing mechanism.
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