Electron transfer in the homodimeric reaction center core complex isolated from Heliobacterium modesticaldum

Abstract

Heliobacteria are strict anaerobic primitive photosynthetic bacteria that have a homodimeric type I reaction center (RC) complex. Their RCs are essentially analogous to the heterodimeric photosystem (PS) I reaction center. The redox components in the electron transfer chain of Heliobacterial RCs are not fully clear yet. We studied the flash-induced ESR signal in the isolated RC core complex of Heliobacterium modesticaldum, which is depleted of iron sulfur centers FA/FB. We detected the transient ESR signals different from those reported in the membrane preparations of this bacterium. The results suggested that the electron transfer pathways are somewhat different between PS I and the Heliobacterial RC.