Non-ionic detergent affects the conformation of a functionally active mutant of Bcl-X_L

Author: Tan, Yee-Joo

Source: Protein Engineering, Volume 13, Number 12, December 2000 , pp. 887-892(6)

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Abstract:

We found that a mutant, Bcl-X<INF>L</INF>(F131V), which was previously reported to have impaired binding capacity, can bind to Bax almost as strongly as wild-type Bcl-X<INF>L</INF>. In the absence of detergent, the Bcl-X<INF>L</INF>(F131V) mutant adopts the same conformation as wild-type Bcl-X<INF>L</INF>, as determined by circular dichroism spectroscopy and size-exclusion chromatography. However, non-ionic detergent induces a conformational change in the Bcl-X<INF>L</INF>(F131V) mutant and causes it to lose Bax-binding capacity. Wild-type Bcl-X<INF>L</INF>, on the other hand, is more resistant to detergent-induced effects and retains its ability to bind Bax in the presence of detergent. Since it has been shown that the Bcl-X<INF>L</INF>(F131V) mutant has nearly the same anti-apoptotic activity as wild-type Bcl-X<INF>L</INF>, it would be likely that the Bcl-X<INF>L</INF>(F131V) mutant can adopt the wild-type conformation, rather than the detergent-induced conformational state and can bind to Bax in vivo. Therefore, our data demonstrated that non-ionic detergent can have unpredicted effects on protein conformation, differential effects on wild-type and mutant Bcl-X<INF>L</INF> proteins in this case and may cause complications in the interpretation of in vitro binding studies.

Keywords: Bcl-2 family; conformation change; non-ionic detergent; protein–protein interactions

Document Type: Research article

Affiliations: 1: Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Republic of Singapore

Publication date: 2000-12-01