期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：7
页码：2824-2829
DOI：10.1073/pnas.0907668107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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 kcat/KM by 250-fold in the proenzyme relative to wild-type barnase. HIV-1 protease cleavage subsequently increases kcat/KM 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.
