Time-resolved step-scan Fourier transform infrared investigation of heme-copper oxidases: implications for O2 input and H2O/H+ output channels

Abstract

We have applied FTIR and time-resolved step-scan Fourier transform infrared (TRS(2)-FTIR) spectroscopy to investigate the dynamics of the heme-Cu(B) binuclear center and the protein dynamics of mammalian aa(3), Pseudomonas stutzeri cbb(3), and caa(3) and ba(3) from Thermus thermophilus cytochrome oxidases. The implications of these results with respect to (1) the molecular motions that are general to the photodynamics of the binuclear center in heme-copper oxidases, and (2) the proton pathways located in the ring A propionate of heme a(3)-Asp372-H(2)O site that is conserved among all structurally known oxidases are discussed.

Nitric oxide activation and reduction by heme–copper oxidoreductases and nitric oxide reductase

“…The A-type heme in cytochrome ba 3 contains a hydrophobic hydroxyethylgeranylgeranyl group which is straight and reaches the cytoplasmic side, without interfering with the proton pathways, instead of a hydroxyethylfarnesyl chain as seen in most bacterial and eucaryotic aa 3 oxidases. Resonance Raman and time-resolved step-scan FTIR spectroscopies have been successfully applied to study the ligand dynamics and the structural and functional relationships of ba 3 and caa 3 oxidoreductases [19][20][21][22][23][24][25][26][27][28]. In this report, the reaction of oxidized Nor and ba 3 with NO will be reviewed.…”

ns-μs Time-Resolved Step-Scan FTIR of ba3 Oxidoreductase from Thermus thermophilus: Protonic Connectivity of w941-w946-w927

“…Based on the crystal structure cytochrome ba 3 from Thermus thermophilus contains a homodinuclear copper center (Cu A ), a low-spin heme b , and a heme a 3 -Cu B center [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. Cytochrome ba 3 catalyzes the reductions of oxygen (O 2 ) to water (H 2 O) and of nitric oxide (NO) to nitrous oxide (N 2 O), as well and the oxidation of carbon monoxide (CO) to carbon dioxide (CO 2 ) [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. The photolyzed ba 3 -CO species is an excellent model for time-resolved spectroscopic studies [7,8,9,13,15,18,24].…”

“…It was concluded that the trans / cis isomerization of the ring-D propionate plays a crucial role in controlling the orientations of “docked” CO between the heme rings-A and -D propionates and that the protein environment removes the barrier to the two orientations of CO [10]. The role of the heme a 3 -D372-H 2 O site and of ring-A propionate as proton carriers to the H 2 O pool, which is conserved among all structurally-known heme-copper oxidases, were reported [11,16,18,23]. The observation of deprotonated and protonated forms of heme a 3 rings-A and -D propionate and D372 indicated a protonic connectivity between the ring-A propionate, a H 2 O molecule and D372.…”

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

“…Nanosecond time-resolution can be accomplished by measuring only the changes in the interferogram, for which a 8-12 bit ADC is sufficient 23,[31][32][33] . Technical aspects 30,34,35 and applications [36][37][38] of time-resolved step-scan have been discussed in detail elsewhere.…”