Structural basis for dimerization of the BNIP3 transmembrane domain.
Structural basis for dimerization of the BNIP3 transmembrane domain.
复制标题
BNIP3 跨膜结构域二聚化的结构基础。
DOI：
10.1021/bi802245u
复制
发表时间：
2009
期刊：
影响因子：
2.9
通讯作者：
Mackenzie,KevinR
中科院分区：
文献类型：
--
作者：
Sulistijo,EndahS;Mackenzie,KevinR
突变数据表明，BNIP3跨膜结构域的二聚化严重依赖于His 173和Ser172之间的氢键，但最近的结构分析表明，这些残基采用多种构象，并不总是氢键的。我们发现，在十二烷基磷胆碱胶束中，BNIP3跨膜区的结构受到磷脂的调节，适当的重组和脂质滴定可以产生一组单一的多肽共振。核磁共振结构测定揭示了一种对称的二聚体，其中所有的界面残基，包括His 173和Ser 172都被很好地定义。小残基Ala 176、Gly 180和Gly 184允许在支持His 173和Ser 172的侧链之间形成单体间氢键的几何图形中接近基本理想的螺旋。大体积残基ILE 177和ILE 181与相对单体的小残基相互作用，界面上有利的极性主链−主链接触可能包括从Gly180到ILE 177的非正则Cα−H·OC氢键。对结构的模拟突变表明，大多数有害的疏水取代消除了His−系列氢键或引入了单体间碰撞，表明立体和氢键在二聚反应的序列依赖性中起着关键作用。大多数非界面位置上的取代不会改变二聚化，但ILE 183上的取代的破坏效应不能用肽−肽接触来解释，因此可能表明该位置上的肽−洗涤剂或肽−脂质相互作用的作用。
Mutagenesis data suggest that BNIP3 transmembrane domain dimerization depends critically on hydrogen bonding between His 173 and Ser 172, but a recent structural analysis indicates that these residues adopt multiple conformations and are not always hydrogen bonded. We show that in dodecylphosphocholine micelles the structure of the BNIP3 transmembrane domain is modulated by phospholipids and that appropriate reconstitution and lipid titration yield a single set of peptide resonances. NMR structure determination reveals a symmetric dimer in which all interfacial residues, including His 173 and Ser 172, are well-defined. Small residues Ala 176, Gly 180, and Gly 184 allow close approach of essentially ideal helices in a geometry that supports intermonomer hydrogen bond formation between the side chains of His 173 and Ser 172. Bulky residues Ile 177 and Ile 181 pack against small residues of the opposite monomer, and favorable polar backbone−backbone contacts at the interface likely include noncanonical Cα−H·OC hydrogen bonds from Gly 180 to Ile 177. Modeling mutations into the structure shows that most deleterious hydrophobic substitutions eliminate the His−Ser hydrogen bond or introduce an intermonomer clash, indicating critical roles for sterics and hydrogen bonding in the sequence dependence of dimerization. Substitutions at most noninterfacial positions do not alter dimerization, but the disruptive effects of substitutions at Ile 183 cannot be rationalized in terms of peptide−peptide contacts and therefore may indicate a role for peptide−detergent or peptide−lipid interactions at this position.