Mcl-1 in complex with Bim BH3 mutant I2dA
[MCL1_HUMAN] Involved in the regulation of apoptosis versus cell survival, and in the maintenance of viability but not of proliferation. Mediates its effects by interactions with a number of other regulators of apoptosis. Isoform 1 inhibits apoptosis. Isoform 2 promotes apoptosis. [B2L11_HUMAN] Induces apoptosis and anoikis. Isoform BimL is more potent than isoform BimEL. Isoform Bim-alpha1, isoform Bim-alpha2 and isoform Bim-alpha3 induce apoptosis, although less potent than isoform BimEL, isoform BimL and isoform BimS. Isoform Bim-gamma induces apoptosis. Isoform Bim-alpha3 induces apoptosis possibly through a caspase-mediated pathway. Isoform BimAC and isoform BimABC lack the ability to induce apoptosis.     
Publication Abstract from PubMed
Mcl-1 is an antiapoptotic Bcl-2-family protein that protects cells against death. Structures of Mcl-1, and of other anti-apoptotic Bcl-2 proteins, reveal a surface groove into which the alpha-helical BH3 regions of certain proapoptotic proteins can bind. Despite high overall structural conservation, differences in this groove afford binding specificity that is important for the mechanism of Bcl-2 family function. We report the crystal structure of human Mcl-1 bound to a BH3 peptide derived from human Bim and the structures for three complexes that accommodate large physicochemical changes at conserved Bim sites. The mutations had surprisingly modest effects on complex stability, and the structures show that Mcl-1 can undergo small changes to accommodate the mutant ligands. For example, a shift in a leucine side chain fills a hole left by an isoleucine-to-alanine mutation at the first hydrophobic buried position of Bim BH3. Larger changes are also observed, with shifting of helix alpha3 accommodating an isoleucine-to-tyrosine mutation at this same position. We surveyed the variation in available Mcl-1 and Bcl-x(L) structures and observed moderate flexibility that is likely critical for facilitating interactions of diverse BH3-only proteins with Mcl-1. With the antiapoptotic Bcl-2 family members attracting significant attention as therapeutic targets, these structures contribute to our growing understanding of how specificity is achieved and can help to guide the design of novel inhibitors that target Mcl-1.
Mcl-1-Bim complexes accommodate surprising point mutations via minor structural changes.,Fire E, Gulla SV, Grant RA, Keating AE Protein Sci. 2010 Jan 11. PMID:20066663
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.