Hu Q, Brunisholz R A, Frank G, Zuber H
Institut für Molekularbiologie und Biophysik, ETH-Hönggerberg, Zürich, Switzerland.
Eur J Biochem. 1996 Jun 1;238(2):381-90. doi: 10.1111/j.1432-1033.1996.0381z.x.
The photoreceptor complex (B885-RC) and the peripheral antenna complex (B800-860) were isolated from photosynthetic membranes of the purple non-sulfur bacterium Rhodocyclus tenuis DSM 109 using a detergent combination of Deriphate-160 and octyl glucoside and subsequent linear sucrose gradient centrifugation. The two complexes were characterized by room-temperature absorption, circular dichroism and fluorescence spectroscopy. The B800-860 complex has a more red-shifted B860 absorbance band. The alpha,beta-polypeptides were purified with a reverse-phase HPLC system and resolved at a ratio of 1:1 in the B800-860 complex and at an overall ratio of 1:1 for the B885-RC complex. The complete amino acid sequences of the alpha and beta polypeptides of the B800-860 and B885-RC complexes were determined by micro-sequencing analysis and mass spectrometry. The B800-860-alpha polypeptide possesses an identical N-terminal domain (the first 15 residues) to Rhodobacter sphaeroides B800-850-alpha polypeptide. The central hydrophobic and C-terminal domains of the B800-860-alpha,beta polypeptides show a number of B870/880-like structural elements in which, of special interest, is the WWSEF cluster in the C-terminal domain of the B800-860-alpha polypeptide which is very similar to the WWEF cluster in the same region of Rhodopseudomonas viridis B1015-alpha polypeptide. The more red-shifted absorption characteristic of the 860-nm bacteriochlorophylls could most probably be related to the B870/880-like polypeptide features in the central hydrophobic domains and the C-terminal domains of the B800-860-alpha,beta polypeptides. The hydropathy plot of the B800-860-alpha polypeptide exhibits an extended C-terminal hydrophobic segment indicative of a second membrane-contacting domain, which has not been found in the antenna polypeptides of the purple bacteria with intracytoplasmic membranes. Further sequence analysis revealed the existence of multiple forms of the B885-alpha,beta polypeptides, the B885-alpha 1,alpha 2 polypeptides, and the B885-beta 1,beta 2 polypeptides. The B885-Alpha 2 polypeptide shows an identical sequence to the B885-alpha 1 polypeptide, but it is 12 amino acid residues shorter than the B885-alpha 1 polypeptide at the C-terminal. The two species of the B885-beta polypeptides were identified as an identical sequence with only one amino acid residue variation at sequence position 34, where the B885-beta 1 has a valine residue and the B885-beta 2 polypeptide an isoleucine residue. The possible correlation between the intensity of the near-infrared circular dichroic signal and the specific structural features of the alpha and beta core antenna polypeptides is also discussed.
使用去垢剂组合Deriphate - 160和辛基葡糖苷以及随后的线性蔗糖梯度离心法，从紫色非硫细菌红环菌（Rhodocyclus tenuis）DSM 109的光合膜中分离出光感受器复合物（B885 - RC）和外周天线复合物（B800 - 860）。通过室温吸收光谱、圆二色光谱和荧光光谱对这两种复合物进行了表征。B800 - 860复合物具有红移程度更大的B860吸收带。α、β多肽通过反相高效液相色谱系统进行纯化，在B800 - 860复合物中α、β多肽的比例为1:1，在B885 - RC复合物中α、β多肽的总体比例为1:1。通过微量测序分析和质谱法确定了B800 - 860和B885 - RC复合物中α和β多肽的完整氨基酸序列。B800 - 860 - α多肽与球形红杆菌（Rhodobacter sphaeroides）B800 - 850 - α多肽具有相同的N端结构域（前15个残基）。B800 - 860 - α、β多肽的中央疏水结构域和C端结构域显示出许多B870/880样的结构元件，其中特别值得关注的是B800 - 860 - α多肽C端结构域中的WWSEF簇，它与绿色红假单胞菌（Rhodopseudomonas viridis）B1015 - α多肽相同区域的WWEF簇非常相似。860 nm细菌叶绿素红移程度更大的吸收特性很可能与B800 - 860 - α、β多肽中央疏水结构域和C端结构域中B870/880样的多肽特征有关。B800 - 860 - α多肽的亲水性图谱显示出一个延伸的C端疏水片段，表明存在第二个膜接触结构域，这在具有胞内膜的紫色细菌的天线多肽中尚未发现。进一步的序列分析揭示了B885 - α、β多肽、B885 - α1、α2多肽以及B885 - β1、β2多肽存在多种形式。B885 - Alpha 2多肽与B885 - α1多肽序列相同，但在C端比B885 - α1多肽短12个氨基酸残基。两种B885 - β多肽被鉴定为序列相同，仅在序列位置34处有一个氨基酸残基差异，其中B885 - β1有一个缬氨酸残基，B885 - β2多肽有一个异亮氨酸残基。还讨论了近红外圆二色信号强度与α和β核心天线多肽的特定结构特征之间可能的相关性。
