X-ray and NMR structure of human Bcl-xL, an inhibitor of programmed cell death

• DOI: 10.1038/381335a0
• Publication Date: 2003-08-12T02:02:55Z
• Authors: Steven W. Muchmore; Michael Sattler; Heng Liang; Robert P. Meadows; John E. Harlan; Ho Sup Yoon; David Nettesheim; Brian S. Chang; Craig B. Thompson; Sui-Lam Wong; Shi-Chung Ng; Stephen W. Fesik
• Keywords: Bcl-2 Family; Bcl-xL; Homology

THE Bcl-2 family of proteins regulate programmed cell death by an unknown mechanism. Here we describe the crystal and solution structures of a Bcl-2 family member, Bcl-xL (ref. 2). The structures consist of two central, primarily hydrophobic alpha-helices, which are surrounded by amphipathic helices. A 60-residue loop connecting helices alpha1 and alpha2 was found to be flexible and non-essential for anti-apoptotic activity. The three functionally important Bcl-2 homology regions (BH1, BH2 and BH3) are in close spatial proximity and form an elongated hydrophobic cleft that may represent the binding site for other Bcl-2 family members. The arrangement of the alpha-helices in Bcl-xL is reminiscent of the membrane translocation domain of bacterial toxins, in particular diphtheria toxin and the colicins. The structural similarity may provide a clue to the mechanism of action of the Bcl-2 family of proteins.