Molecular Basis for Membrane Pore Formation by Bax Protein Carboxyl Terminus

    Authors

    S. A. Tatulian; P. Garg; K. N. Nemec; B. Chen;A. R. Khaled

    Comments

    Authors: contact us about adding a copy of your work at STARS@ucf.edu

    Abbreviated Journal Title

    Biochemistry

    Keywords

    TRANSFORM INFRARED-SPECTROSCOPY; ANGLE-SPINNING NMR; SECONDARY; STRUCTURE; CELL-DEATH; ANTIMICROBIAL PEPTIDES; CIRCULAR-DICHROISM; LIPID-MEMBRANES; HYDROGEN-BONDS; PERMEABILIZATION; CONFORMATION; Biochemistry & Molecular Biology

    Abstract

    Box protein plays a key role in mitochondrial membrane permeabilization and cytochrome c release upon apoptosis. Our recent data have indicated that the 20-residue C-terminal peptide of Box (BaxC-KK; VTIFVAGVL-TASLTIWKKMG), when expressed intracellularly, translocates to the mitochondria and exerts lethal effect on cancer cells. Moreover, the BaxC-KK peptide, as well as two mutants where the two lysines are replaced with glutamate (BaxC-EE) or leucine (BaxC-LL), have been shown to form relatively large pores in lipid membranes, composed of up to eight peptide molecules per pore. Here the pore structure is analyzed by polarized Fourier transform infrared, circular dichroism, and fluorescence experiments on the peptides reconstituted in phospholipid membranes. The peptides assume an alpha/beta-type secondary structure within membranes. Both beta-strands and alpha-helices are significantly (by 30-60 deg) tilted relative to the membrane normal. The tryptophan residue embeds into zwitterionic membranes at 8-9 angstrom from the membrane center. The membrane anionic charge causes a deeper insertion of tryptophan for BaxC-KK and BaxC-LL but not for BaxC-EE. Combined with the pore stoichiometry determined earlier, these structural constraints allow construction of a model of the pore where eight peptide molecules form an "alpha/beta-ring" structure within the membrane. These results identify a strong membranotropic activity of Box C-terminus and propose a new mechanism by which peptides can efficiently perforate cell membranes. Knowledge on the pore forming mechanism of the peptide may facilitate development of peptide-based therapies to kill cancer or other detrimental cells such as bacteria or fungi.

    Journal Title

    Biochemistry

    Volume

    51

    Issue/Number

    46

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    9406

    Last Page

    9419

    WOS Identifier

    WOS:000311858400016

    ISSN

    0006-2960

    Share

    COinS