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Specificity of helix packing in transmembrane dimer of the cell death factor BNIP3: A molecular modeling study
Author(s) -
Vereshaga Yana A.,
Volynsky Pavel E.,
Pustovalova Julia E.,
Nolde Dmitry E.,
Arseniev Alexander S.,
Efremov Roman G.
Publication year - 2007
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21555
Subject(s) - dimer , molecular dynamics , transmembrane domain , chemistry , helix (gastropod) , crystallography , lipid bilayer , transmembrane protein , bilayer , biophysics , membrane , computational chemistry , biology , biochemistry , ecology , receptor , organic chemistry , snail
BNIP3 is a mitochondrial 19‐kDa proapoptotic protein, a member of the Bcl‐2 family. It has a single COOH‐terminal transmembrane (TM) α‐helical domain, which is required for membrane targeting, proapoptotic activity, hetero‐ and homo‐dimerization in membrane. The role and the molecular details of association of TM helices of BNIP3 are yet to be established. Here, we present a molecular modeling study of helix interactions in its membrane domain. The approach combines Monte Carlo conformational search in an implicit hydrophobic slab followed by molecular dynamics simulations in a hydrated full‐atom lipid bilayer. The former technique was used for exhaustive sampling of the peptides' conformational space and for generation of putative “native‐like” structures of the dimer. The latter ones were taken as realistic starting points to assess stability and dynamic behavior of the complex in explicit lipid–water surrounding. As a result, several groups of tightly packed right‐handed structures of the dimer were proposed. They have almost similar helix–helix interface, which includes the motif A 176 xxxG 180 xxxG 184 and agrees well with previous mutagenesis data and preliminary NMR analysis. Molecular dynamics simulations of these structures reveal perfect adaptation of most of them to heterogeneous membrane environment. A remarkable feature of the predicted dimeric structures is the occurrence of a cluster of H‐bonded histidine 173 and serines 168 and 172 on the helix interface, near the N‐terminus. Because of specific polar interactions between the monomers, this part of the dimer has no such dense packing as the C‐terminal one, thus allowing penetration of water from the extramembrane side into the membrane interior. We propose that the ionization state of His 173 can mediate structural and dynamic properties of the dimer. This, in turn, may be related to pH‐dependent proapoptotic activity of BNIP3, which is triggering on by acidosis appearing under hypoxic conditions. Proteins 2007. © 2007 Wiley‐Liss, Inc.