Abstract
We have prepared two Fds (FdA, B) from Heliobacillus mobilis and determined their N-terminal amino acid sequences. FdB is sensitive to oxygen, its A385 value being halved in 2 hours at 4oC under air. On the other hand, the A385 of FdA was not decreased during 20 hours under the above conditions. We have also determined the nucleotide sequences of these Fd genes. The two Fd genes are arranged in tandem. The sequences of FdA and FdB show high similarity with those of clostridial Fds and proteobacterial Fds, respectively. In the presence of Chlorobium tepidum RC and spinach FNR, FdA and FdB supported NADP+ photoreduction, but the rates were about 60% and 30% of those supported by C. tepidum Fd, respectively. RC particles were solubilized from membranes of H. mobilis with detergents, and partially purified by sucrose-density ultracentrifugation and by anion-exchange chromatography. The RC preparation photoreduced C. tepidum Fd.
