Di Paolo Roberto E, Pereira Patrícia M, Gomes Inês, Valente Filipa M A, Pereira Inês A C, Franco Ricardo
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, Av. da República, 2781-901 Oeiras, Portugal.
J Biol Inorg Chem. 2006 Mar;11(2):217-24. doi: 10.1007/s00775-005-0067-4. Epub 2005 Dec 10.
Resonance Raman (RR) spectroscopy was used to investigate conformational characteristics of the hemes of several ferricytochromes of the cytochrome c3 family, electron transfer proteins isolated from the periplasm and membranes of sulfate-reducing bacteria. Our analysis concentrated on the low-frequency region of the RR spectra, a fingerprint region that includes vibrations for heme-protein C-S bonds [nu(C(a)S)]. It has been proposed that these bonds are directly involved in the electron transfer process. The three groups of tetraheme cytochrome c3 analyzed, namely Type I cytochrome c (3) (TpIc (3)s), Type II cytochrome c (3) (TpIIc (3)s) and Desulfomicrobium cytochromes c3, display different frequency separations for the two nu(C(a)S) lines that are similar among members of each group. These spectral differences correlate with differences in protein structure observed among the three groups of cytochromes c3. Two larger cytochromes of the cytochrome c3 family display RR spectral characteristics for the nu(C(a)S) lines that are closer to TpIIc3 than to TpIc3. Two other multiheme cytochromes from Desulfovibrio that do not belong to the cytochrome c3 family display nu(C(a)S) lines with reverse relative areas in comparison with the latter family. This RR study shows that the small differences in protein structure observed among these cytochrome c3 correlate to differences on the heme-protein bonds, which are likely to have an impact upon the protein function, making RR spectroscopy a sensitive and useful tool for characterizing these cytochromes.
共振拉曼（RR）光谱法被用于研究细胞色素c3家族中几种高铁细胞色素的血红素的构象特征，这些细胞色素是从硫酸盐还原菌的周质和膜中分离出来的电子传递蛋白。我们的分析集中在RR光谱的低频区域，这是一个指纹区域，包括血红素-蛋白质C-S键[ν(C(a)S)]的振动。有人提出这些键直接参与电子传递过程。所分析的三组四血红素细胞色素c3，即I型细胞色素c(3)（TpIc(3)s）、II型细胞色素c(3)（TpIIc(3)s）和脱硫微球菌细胞色素c3，每组成员之间相似的两条ν(C(a)S)谱线显示出不同的频率间隔。这些光谱差异与三组细胞色素c3中观察到的蛋白质结构差异相关。细胞色素c3家族的另外两种较大的细胞色素显示出的ν(C(a)S)谱线的RR光谱特征更接近TpIIc3而不是TpIc3。来自脱硫弧菌的另外两种不属于细胞色素c3家族的多血红素细胞色素，其ν(C(a)S)谱线的相对面积与后一个家族相比是相反的。这项RR研究表明，在这些细胞色素c3中观察到的蛋白质结构的微小差异与血红素-蛋白质键的差异相关，这可能会对蛋白质功能产生影响，使得RR光谱法成为表征这些细胞色素的一种灵敏且有用的工具。
