Gall A, Fowler G J, Hunter C N, Robert B
Section de Biophysique des Protéines et des Membranes, DBCM CEA and URA 2096 CNRS, C. E. Saclay, 91191 Gif-sur-Yvette Cedex, France.
Biochemistry. 1997 Dec 23;36(51):16282-7. doi: 10.1021/bi9717237.
Resonance Raman spectroscopy was performed on peripheral light-harvesting proteins from Rhodobacter sphaeroides in which the residue betaArg-10 has been modified by site-selected mutagenesis. We show that this residue is indeed involved (as proposed by X-ray crystallographic studies on the LH2 complex from Rhodopseudomonas acidophila), in an H-bond with the acetyl carbonyl of the 800 nm-absorbing BChl in these proteins (B800), and that the presence of such an H-bond induces a ca. 10 nm red shift of the lowest energy transition (Qy) of this molecule. Moreover, other parameters involved in the fine tuning of the absorption of the B800 molecules may be determined from our experiments, and we propose that the local electromagnetic properties of the B800 binding site may induce an additional 10 nm red shift of this transition. These results constitute the first experimental evidence for the parameters able to modify in vivo the absorption of "monomeric" BChl molecules, i.e. BChl not involved in strong excitonic interactions, and will be of great help for understanding the absorption properties of such pigments in other light-harvesting systems.
对球形红细菌的外周捕光蛋白进行了共振拉曼光谱分析，其中β-精氨酸-10残基已通过定点诱变进行了修饰。我们表明，该残基确实如对嗜酸红假单胞菌LH2复合物的X射线晶体学研究所提出的那样，与这些蛋白质中800 nm吸收的细菌叶绿素（B800）的乙酰羰基形成氢键，并且这种氢键的存在会使该分子最低能量跃迁（Qy）发生约10 nm的红移。此外，我们的实验可以确定参与B800分子吸收精细调节的其他参数，并且我们提出B800结合位点的局部电磁特性可能会使该跃迁额外发生10 nm的红移。这些结果构成了能够在体内改变“单体”细菌叶绿素分子（即不参与强激子相互作用的细菌叶绿素）吸收的参数的首个实验证据，并且将对理解此类色素在其他捕光系统中的吸收特性有很大帮助。
