Different structural changes occur in blue- and green-proteorhodopsins during the primary photoreaction.
Journal Article (Journal Article)
We examine the structural changes during the primary photoreaction in blue-absorbing proteorhodopsin (BPR), a light-driven retinylidene proton pump, using low-temperature FTIR difference spectroscopy. Comparison of the light-induced BPR difference spectrum recorded at 80 K to that of green-absorbing proteorhodopsin (GPR) reveals that there are several differences in the BPR and GPR primary photoreactions despite the similar structure of the retinal chromophore and all-trans --> 13-cis isomerization. Strong bands near 1700 cm(-1) assigned previously to a change in hydrogen bonding of Asn230 in GPR are still present in BPR. However, additional bands in the same region are assigned on the basis of site-directed mutagenesis to changes occurring in Gln105. In the amide II region, bands are assigned on the basis of total (15)N labeling to structural changes of the protein backbone, although no such bands were previously observed for GPR. A band at 3642 cm(-1) in BPR, assigned to the OH stretching mode of a water molecule on the basis of H2(18)O substitution, appears at a different frequency than a band at 3626 cm(-1) previously assigned to a water molecule in GPR. However, the substitution of Gln105 for Leu105 in BPR leads to the appearance of both bands at 3642 and 3626 cm(-1), indicating the waters assigned in BPR and GPR exist in separate distinct locations and can coexist in the GPR-like Q105L mutant of BPR. These results indicate that there exist significant differences in the conformational changes occurring in these two types proteorhodopsin during the initial photoreaction despite their similar chromophore structures, which might reflect a different arrangement of water in the active site as well as substitution of a hydrophilic for hydrophobic residue at residue 105.
Full Text
Duke Authors
Cited Authors
- Amsden, JJ; Kralj, JM; Bergo, VB; Spudich, EN; Spudich, JL; Rothschild, KJ
Published Date
- November 2008
Published In
Volume / Issue
- 47 / 44
Start / End Page
- 11490 - 11498
PubMed ID
- 18842006
Pubmed Central ID
- PMC3631532
Electronic International Standard Serial Number (EISSN)
- 1520-4995
International Standard Serial Number (ISSN)
- 0006-2960
Digital Object Identifier (DOI)
- 10.1021/bi800945t
Language
- eng