A Fourier transform infrared study of Neurospora rhodopsin: similarities with archaeal rhodopsins.
The NOP-1 gene from the eukaryote Neurospora crassa, a filamentous fungus, has recently been shown to encode an archaeal rhodopsin-like protein NOP-1. To explore the functional mechanism of NOP-1 and its possible similarities to archaeal and visual rhodopsins, static and time-resolved Fourier transform infrared difference spectra were measured from wild-type NOP-1 and from a mutant containing an Asp-->Glu substitution in the Schiff base (SB) counterion, Asp131 (D131E). Several conclusions could be drawn about the molecular mechanism of NOP-1: (1) the NOP-1 retinylidene chromophore undergoes an all-trans to 13-cis isomerization, which is typical of archaeal rhodopsins, and closely resembles structural changes of the chromophore in sensory rhodopsin II; (2) the NOP-1 SB counterion, Asp131, has a very similar environment and behavior compared with the SB counterions in bacteriorhodopsin (BR) and sensory rhodopsin II; (3) the O-H stretching of a structurally active water molecule(s) in NOP-1 is similar to water detected in BR and is most likely located near the SB and SB counterion in these proteins; and (4) one or more cysteine residues undergo structural changes during the NOP-1 photocycle. Overall, these results indicate that many features of the active sites of the archaeal rhodopsins are conserved in NOP-1, despite its eukaryotic origin.
Bergo
Vladislav
V
Department of Physics, Molecular Biophysics Laboratory, Boston University, Boston, MA 02215, USA.
Spudich
Elena N
EN
Spudich
John L
JL
Rothschild
Kenneth J
KJ
D001105:Archaea / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D008968:Molecular Conformation; D009491:Neurospora / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D002264:Carboxylic Acids; D012243:Rhodopsin