College of Chemistry and Chemical Engineering, Qiqihar University, No. 42, Wenhua Street, Qiqihar, PR China.
College of Chemistry and Chemical Engineering, Qiqihar University, No. 42, Wenhua Street, Qiqihar, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Mar 25;122:82-92. doi: 10.1016/j.saa.2013.11.033. Epub 2013 Nov 16.
Slc11a1 is a divalent metal cation transporter with 12 putative transmembrane domains (TM) and plays a role in host defense. In present work, we investigated the secondary structure and topology of the peptides associated to Slc11a1-TM2, TM3 and TM4 (wildtype peptides and function-relating mutants) in the phospholipid vesicles (DMPC, DMPG and their mixtures) using circular dichroism, fluorescence spectroscopy and differential scanning calorimetry. We found that TM3 is obviously different in secondary structure and topology from TM2 to TM4 in the lipid membranes. The peptide TM3 is less structured and embedded in the lipid membranes less deeply than TM2 and TM4 at pH 5.5 and 7. The insertion position of TM3 in the lipid membranes is adjusted by pH, more deeply at more acidic pH environment, whereas the locations of TM2 and TM4 in the lipid membranes are less changed with pH. The E139A substitution of TM3 significantly impairs the pH dependence of the buried depth of TM3 and causes a pronounced increase in helicity in all DMPG-containing lipid vesicles at pH 5.5 and 7 and in DMPC at pH 4. In contrast, TM2 and TM4 are similar in topology. The G169D mutation has little effect on the topological arrangement of TM4 in membranes. The property of headgroups of the phospholipids has an effect on the secondary structure and topology of the peptides. All peptides could be structured with more helicity and embedded more deeply in DMPG-containing lipid vesicles than in DMPC membrane at pH 5.5 and 7.
Slc11a1 是一种二价金属阳离子转运蛋白，具有 12 个假定的跨膜结构域（TM），在宿主防御中发挥作用。在本工作中，我们使用圆二色性、荧光光谱和差示扫描量热法研究了与 Slc11a1-TM2、TM3 和 TM4（野生型肽和功能相关的突变体）相关的肽在磷脂囊泡（DMPC、DMPG 及其混合物）中的二级结构和拓扑结构。我们发现，在脂质膜中，TM3 的二级结构和拓扑结构明显不同于 TM2 到 TM4。在 pH 5.5 和 7 时，肽 TM3 的结构较少，在脂质膜中嵌入的深度也较 TM2 和 TM4 浅。TM3 在脂质膜中的插入位置受 pH 调节，在更酸性的 pH 环境中插入更深，而 TM2 和 TM4 在脂质膜中的位置随 pH 变化较小。TM3 的 E139A 取代显著破坏了 TM3 埋藏深度的 pH 依赖性，并在 pH 5.5 和 7 时在所有含有 DMPG 的脂质囊泡中和在 pH 4 时在 DMPC 中导致 TM3 的螺旋度显著增加。相比之下，TM2 和 TM4 的拓扑结构相似。TM4 中的 G169D 突变对膜中 TM4 的拓扑排列几乎没有影响。磷脂头部基团的性质对肽的二级结构和拓扑结构有影响。所有肽在 pH 5.5 和 7 时在含有 DMPG 的脂质囊泡中都能形成更多的螺旋结构，并比在 DMPC 膜中嵌入得更深。
