Photo-dynamics of photoactivated adenylyl cyclase TpPAC from the spirochete bacterium Turneriella parva strain H-T

摘要

The photoactivated adenylyl cydase TpPAC from the spirochete bacterium Turneriella parva was synthesized and the purified recombinant protein was characterized by biochemical and optical spectroscopic method's. TpPAC consists of a BLUF domain (BLUF = Blue Light sensor Using Flavin) and an adenylyl cyclase homology domain (CHD). A light induced cAMP cyclase activity of approximate to 53.3 nmol mg(-1) min(-1) was measured while in the dark the cyclase activity was approximately a factor of 240 lower. The photo-cycling dynamics of the BLUF domain of TpPAC was studied by absorption spectra, fluorescence quantum distribution, and fluorescence lifetime measurements. The quantum efficiency of BLUF domain signaling state formation was found to be phi(s) approximate to 0.59. A three-component exponential recovery of the signaling state to the receptor state was observed with the time constants tau(rec,1) = 4.8 s, tau(rec,2) = 34.2 s, and tau(rec,3) = 293 s at 21.3 degrees C The protein thermal stability was studied by stepwise sample heating and cooling. An apparent TpPAC melting temperature of v(m) approximate to 46 degrees C was determined. The photo-degradation of TpPAC in the signaling state was studied by prolonged intense light exposure at 455 nm. An irreversible flavin photo-degradation was observed with quantum yield phi(D) approximate to 8.7 x 10(-6). (C) 2015 Elsevier B.V. All rights reserved.