Rosen D, Okamura M Y, Abresch E C, Valkirs G E, Feher G
Biochemistry. 1983 Jan 18;22(2):335-41. doi: 10.1021/bi00271a016.
The location of the cytochrome binding site on the reaction center of Rhodopseudomonas sphaeroides was studied by two different approaches. In one, cross-linking agents, principally dithiobis(propionimidate) and dimethyl suberimidate, were used to link cytochrome c and cytochrome c2 to reaction centers; in the other, the inhibition of electron transfer by antibodies against the subunits was investigated. Cytochrome c (horse) cross-linked to the L and M subunits, whereas cytochrome c2 (R. sphaeroides) cross-linked only to the L subunit. The cross-linked reaction center-cytochrome complexes were isolated by affinity chromatography. The rate of electron transfer in the cross-linked cytochrome c2 complex was the same as that in the un-cross-linked complex. However, when cytochrome c was used, the rate in the cross-linked complex was about 15 times slower than that in the un-cross-linked complex. Fab fragments of antibodies specific against the L and M subunits blocked electron transfer from both cytochrome c (horse) and cytochrome c2 (R. sphaeroides). Antibodies specific for the H subunit did not block either reaction. We conclude that the cytochrome binding site on the reaction center is close (approximately 10 A) to both the L and M subunits, possibly in a cleft between them.
通过两种不同的方法研究了球形红假单胞菌反应中心上细胞色素结合位点的位置。一种方法是，主要使用交联剂二硫代双（丙亚氨酸酯）和亚辛二酸二甲酯将细胞色素c和细胞色素c2与反应中心连接；另一种方法是，研究针对亚基的抗体对电子传递的抑制作用。细胞色素c（马）与L和M亚基交联，而细胞色素c2（球形红假单胞菌）仅与L亚基交联。通过亲和色谱法分离交联的反应中心-细胞色素复合物。交联的细胞色素c2复合物中的电子传递速率与未交联的复合物中的相同。然而，当使用细胞色素c时，交联复合物中的速率比未交联复合物中的速率慢约15倍。针对L和M亚基的特异性抗体的Fab片段阻断了来自细胞色素c（马）和细胞色素c2（球形红假单胞菌）的电子传递。针对H亚基的特异性抗体没有阻断任何一个反应。我们得出结论，反应中心上的细胞色素结合位点与L和M亚基都很近（约10埃），可能在它们之间的裂隙中。
