Abstract:
:The photocycle of the photophobic receptor sensory rhodopsin II from N. pharaonis was analyzed by varying measuring wavelengths, temperature, and pH, and by exchanging H2O with D2O. The data can be satisfactorily modeled by eight exponents over the whole range of modified parameters. The kinetic data support a model similar to that of bacteriorhodopsin (BR) if a scheme of irreversible first-order reactions is assumed. Eight kinetically distinct protein states can then be identified. These states are formed from five spectrally distinct species. The chromophore states Si correspond in their spectral properties to those of the BR photocycle, namely pSRII510 (K), pSRII495 (L), pSRII400 (M), pSRII485 (N), and pSRII535 (O). In comparison to BR, pSRII400 is formed approximately 10 times faster than the M state; however, the back-reaction is almost 100 times slower. Comparison of the temperature dependence of the rate constants with those from the BR photocycle suggests that the differences are caused by changes of DeltaS. The rate constants of the pSRII photocycle are almost insensitive to the pH variation from 9.0 to 5.5, and show only a small H2O/D2O effect. This analysis supports the idea that the conformational dynamics of pSRII controls the kinetics of the photocycle of pSRII.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Chizhov I,Schmies G,Seidel R,Sydor JR,Lüttenberg B,Engelhard Mdoi
10.1016/S0006-3495(98)77588-5subject
Has Abstractpub_date
1998-08-01 00:00:00pages
999-1009issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(98)77588-5journal_volume
75pub_type
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