Document Detail


Structural changes during the photocycle of photoactive yellow protein monitored by ultraviolet resonance raman spectra of tyrosine and tryptophan.
MedLine Citation:
PMID:  16375346     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Photoactive yellow protein (PYP) is a bacterial blue light photoreceptor, and photoexcitation of dark-state PYP (PYP(dark)) triggers a photocycle that involves several intermediate states. We report the ultraviolet resonance Raman spectra of PYP with 225-250 nm excitations and investigate protein structural changes accompanying the formation of the putative signaling state denoted PYP(M). The PYP(M)-PYP(dark) difference spectra show several features of tyrosine and tryptophan, indicating environmental changes for these amino acid residues. The tyrosine difference signals show small upshifts with intensity changes in Y8a and Y9a bands. Although there are five tyrosine residues in PYP, Tyr42 and Tyr118 are suggested to be responsible for the difference signals on the basis of a global fitting analysis of the difference spectra at different excitation wavelengths and the crystal structure of PYP(dark). A further experiment on the Thr50-->Val mutant supports environmental changes in Tyr42. The observed upshift of the Y8a band suggests a weaker or broken hydrogen bond between Tyr42 and the chromophore in PYP(M). In addition, a reorientation of the OH group in Tyr42 is suggested from the upshift of the Y9a band. For tryptophan, the Raman bands of W3, W16, and W18 modes diminish in intensity upon formation of PYP(M). The loss of intensities is attributable to an exposure of tryptophan in PYP(M). PYP contains only one tryptophan (Trp119) that is located more than 10 A from the active site. Thus the observed changes are indicative of global conformational changes in protein during the transition from PYP(dark) to PYP(M). These results are in line with the currently proposed photocycle mechanism of PYP.
Authors:
Samir F El-Mashtoly; Seigo Yamauchi; Masato Kumauchi; Norio Hamada; Fumio Tokunaga; Masashi Unno
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  109     ISSN:  1520-6106     ISO Abbreviation:  J Phys Chem B     Publication Date:  2005 Dec 
Date Detail:
Created Date:  2005-12-26     Completed Date:  2006-07-25     Revised Date:  2007-03-23    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  23666-73     Citation Subset:  IM    
Affiliation:
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
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MeSH Terms
Descriptor/Qualifier:
Bacterial Proteins / chemistry*,  genetics
Models, Molecular
Mutation
Photochemistry
Photoreceptors, Microbial / chemistry*,  genetics
Protein Structure, Secondary
Spectrophotometry, Ultraviolet
Spectrum Analysis, Raman
Tryptophan / chemistry*
Tyrosine / chemistry*
Chemical
Reg. No./Substance:
0/Bacterial Proteins; 0/Photoreceptors, Microbial; 0/photoactive yellow protein, Bacteria; 55520-40-6/Tyrosine; 73-22-3/Tryptophan

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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