Photoinduced formation of flavin radicals in BLUF domains lacking the central glutamine

作者：Fudim Roman; Mehlhorn Jennifer; Berthold Thomas; Weber Stefan; Schleicher Erik; Kennis John T M; Mathes Tilo^*

来源：FEBS Journal, 2015, 282(16): 3161-3174.

DOI：10.1111/febs.13297

• flavin
• photoreceptor
• proton-coupled electron transfer
• spin-correlated radical pair
• ultrafast spectroscopy

Blue light receptors using FAD (BLUFs) facilitate blue light-induced signal transduction via light-induced rearrangement of hydrogen bonds between the flavin chromophore and a conserved glutamine side chain. Here, we investigated the photochemistry of the BLUF domain Slr1694 from Synechocystis sp. in which the glutamine side chain was removed. Without the glutamine, no red-shifted signaling state is formed, but light-induced proton-coupled electron transfer between protein and flavin takes place similarly as for the wild-type protein. However, the lifetime of the neutral flavin semiquinone-tyrosyl radical pair is greatly prolonged from <100ps to several nanoseconds, which indicates that the formation of radical intermediates drives the hydrogen bond rearrangement in BLUF photoactivation. Moreover, glutamine plays a central role in the molecular organization of the hydrogen bond network in the flavin-binding pocket, as its removal enhances electron transfer from tyrosine to the excited flavin, and enables competing electron transfer from a nearby tryptophan.

• 出版日期2015-8