Document Detail

Fine tuning of the spectral properties of LH2 by single amino acid residues.
MedLine Citation:
PMID:  18365764     Owner:  NLM     Status:  MEDLINE    
The peripheral light-harvesting complex, LH2, of Rhodobacter sphaeroides consists of an assembly of membrane-spanning alpha and beta polypeptides which assemble the photoactive bacteriochlorophyll and carotenoid molecules. In this study we systematically investigated bacteriochlorophyll-protein interactions and their effect on functional bacteriochlorophyll assembly by site-directed mutations of the LH2 alpha-subunit. The amino acid residues, isoleucine at position -1 and serine at position -4 were replaced by 12 and 13 other residues, respectively. All residues replacing isoleucine at position -1 supported the functional assembly of LH2. The replacement of isoleucine by glycine, glutamine or asparagine, however, produced LH2 complex with significantly altered spectral properties in comparison to LH2 WT. As indicated by resonance Raman spectroscopy extensive rearrangement of the bacteriochlorophyll-B850 macrocycle(s) took place in LH2 in which isoleucine -1 was replaced by glycine. The replacement results in disruption of the H-bond between the C3 acetyl groups and the aromatic residues +13/+14 without affecting the H-bond involving the C13(1) keto group. In contrast, nearly all amino acid replacements of serine at position -4 resulted in shifting of the bacteriochlorophyll-B850 red most absorption maximum. Interestingly, the extent of shifting closely correlated with the volume of the residue at position -4. These results illustrate that fine tuning of the spectral properties of the bacteriochlorophyll-B850 molecules depend on their packing with single amino acid residues at distinct positions.
Martina V Silber; Günther Gabriel; Brigitte Strohmann; Adela Garcia-Martin; Bruno Robert; Paula Braun
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-03-26
Journal Detail:
Title:  Photosynthesis research     Volume:  96     ISSN:  0166-8595     ISO Abbreviation:  Photosyn. Res.     Publication Date:  2008 May 
Date Detail:
Created Date:  2008-04-09     Completed Date:  2008-07-21     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100954728     Medline TA:  Photosynth Res     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  145-51     Citation Subset:  IM    
Department Biologie I, Ludwig-Maximilians-Universität München, Bereich Botanik, Menzinger Str. 67, 80638 München, Germany.
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MeSH Terms
Amino Acids / chemistry,  genetics,  metabolism*
Bacterial Proteins / chemistry,  genetics,  metabolism*
Light-Harvesting Protein Complexes / chemistry,  genetics,  metabolism*
Mutagenesis, Site-Directed
Protein Conformation
Protein Denaturation
Rhodobacter sphaeroides / genetics,  metabolism*
Reg. No./Substance:
0/Amino Acids; 0/Bacterial Proteins; 0/Light-Harvesting Protein Complexes

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