Department of Biology, Washington University in St. Louis, 1 Brookings Drive, St. Louis, MO, 63130, USA.
Photosynthetic Antenna Research Center (PARC), Washington University in St. Louis, 1 Brookings Drive, St. Louis, MO, 63130, USA.
Photosynth Res. 2019 Apr;140(1):39-49. doi: 10.1007/s11120-018-0591-z. Epub 2018 Oct 12.
The trimeric nature of the Fenna-Matthews-Olson (FMO) protein antenna complex from green sulfur phototrophic bacteria was investigated. Mutations were introduced into the protein at positions 142 and 198, which were chosen to destabilize the intra-trimer salt bridges between adjacent monomers. Strains bearing the mutations R142L, R198L, or their combination, exhibited altered optical absorption spectra of purified membranes and fluoresced more intensely than the wild type. In particular, the introduction of the R142L mutation resulted in slower culture growth rates, as well as an FMO complex that was not able to be isolated in appreciable quantities, while the R198L mutation yielded an FMO complex with increased sensitivity to sodium thiocyanate and Triton X-100 treatments. Native and denaturing PAGE experiments suggest that much of the FMO complexes in the mutant strains pool with the insoluble material upon membrane solubilization with n-dodecyl β-D-maltoside, a mild nonionic detergent. Taken together, our results suggest that the quaternary structure of the FMO complex, the homotrimer, is an important factor in the maintenance of the complex's tertiary structure.
我们研究了来自绿硫光合细菌的 Fenna-Matthews-Olson (FMO) 蛋白天线复合物的三聚体性质。在位置 142 和 198 处引入了突变，这些突变被选择来破坏相邻单体之间的三聚体盐桥的稳定性。携带 R142L、R198L 或其组合突变的菌株表现出纯化膜的光学吸收光谱发生改变，并且比野生型更强烈地荧光。特别是，引入 R142L 突变会导致培养物生长速度变慢，并且无法分离出可观数量的 FMO 复合物，而 R198L 突变会导致 FMO 复合物对硫氰酸钠和 Triton X-100 处理的敏感性增加。天然和变性 PAGE 实验表明，在使用温和的非离子去污剂正十二烷基-β-D-麦芽糖苷溶解膜时，突变株中的大部分 FMO 复合物与不溶性物质一起在聚集体中。总之，我们的结果表明，FMO 复合物的四级结构，即同源三聚体，是维持复合物三级结构的重要因素。
