Abstract:
:The time-resolved thermodynamics of the flavin mononucleotide (FMN)-binding LOV1 domain of Chlamydomonas reinhardtii phot (phototropin homolog) was studied by means of laser-induced optoacoustic spectroscopy. In the wild-type protein the early red-shifted intermediate LOV(715) exhibits a small volume contraction, DeltaV(715) = -1.50 ml/mol, with respect to the parent state. LOV(715) decays within few micro s into the covalent FMN-Cys-57 adduct LOV(390), that shows a larger contraction, DeltaV(390) = -8.8 ml/mol, suggesting a loss of entropy and conformational flexibility. The high energy content of LOV(390), E(390) = 180 kJ/mol, ensures the driving force for the completion of the photocycle and points to a strained photoreceptor conformation. In the LOV-C57S mutated protein the photoadduct is not formed and DeltaV(390) is undetected. Large effects on the measured DeltaVs are observed in the photochemically competent R58K and R58K/D31Q mutated proteins, with DeltaV(390) = -2.0 and -1.9 ml/mol, respectively, and DeltaV(715) approximately 0. The D31Q and D31N substitutions exhibit smaller but well-detectable effects. These results show that the photo-induced volume changes involve the protein region comprising Arg-58, which tightly interacts with the FMN phosphate group.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Losi A,Kottke T,Hegemann Pdoi
10.1016/S0006-3495(04)74180-6subject
Has Abstractpub_date
2004-02-01 00:00:00pages
1051-60issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(04)74180-6journal_volume
86pub_type
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