Conformational changes during apoplastocyanin folding observed by photocleavable modification and transient grating.
J Am Chem Soc
; 128(23): 7551-8, 2006 Jun 14.
Article
in En
| MEDLINE
| ID: mdl-16756310
ABSTRACT
A new method to investigate the initial protein folding dynamics is developed based on a pulsed laser light triggering method and a unique transient grating method. The side chain of the cysteine residue of apoplastocyanin (apoPC) was site-specifically modified with a 4,5-dimethoxy-2-nitrobenzyl derivative, where the CD and 2D NMR spectra showed that the modified apoPC was unfolded. The substituent was cleaved with a rate of about 400 ns by photoirradiation, which was monitored by the disappearance of the absorption band at 355 nm and the increase in the transient grating signal. After a sufficient time from the photocleavage reaction, the CD and NMR spectra showed that the native beta-sheet structure was recovered. Protein folding dynamics was monitored in the time domain with the transient grating method from a viewpoint of the molecular volume change and the diffusion coefficient, both of which reflect the global structural change, including the protein-water interaction. The observed volume decrease of apoPC with a time scale of 270 micros is ascribed to the initial hydrophobic collapse. The increase in the diffusion coefficient (23 ms) is considered to indicate a change from an intermolecular to an intramolecular hydrogen bonding network. The initial folding process of apoPC is discussed based on these observations.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Apoproteins
/
Plastocyanin
/
Protein Conformation
/
Protein Structure, Secondary
/
Protein Folding
/
Light
Language:
En
Journal:
J Am Chem Soc
Year:
2006
Document type:
Article
Affiliation country:
Japan