Molecular organisation of the chlorophyll a/c light-harvesting complex of Pleurochloris meiringensis (Xanthophyceae). Pigment binding and secondary structure of the protein

✍ Scribed by C. Büchel; G. Garab

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 357 KB
• Volume: 42
• Category: Article
• ISSN: 1011-1344
• DOI: 10.1016/s1011-1344(98)00069-4

✦ Synopsis

In our previous study by means of circular dichroism (CI) ) spectroscopy we have shown thal the pigmenl c~rganisation in the chlorophyll aA' light harvesting complex ( Chl a/c LHC ) isolated fl-om Pletoochlori.~ ;;;ei;'i~w';~i.s signilicantly differs from the architecture of the main Chl a/b light harvesting antenna complexes of higher plants ( Bhchel and Garab. J. Photochem. Photobiol.. B: Biol.. 37 ( 1997 } 1 I 8--124 ). In this work we measured the CD spectra in the far-UV, between 190 nm and 240 urn. and investigated the '~aliaUons of the secondary structure of the protein upon treatments which affect the binding of the long wavelength Chl a. We found thai low concentrations ( < 5~/~ ) of acetone, which had no noticeable effect on tile ( -)679 nm CD band. drastically reduced the {,-helical content of the protein. In contrast, amounts of digitonin, which completely abolished this intense, non-conservative CD b:md of Chl a, induced only minor changes in tile secondary slructure of the prolein complex. These data suggest thai the binding site of the hmg-wavelength absorbing Chl o is found in a position deeply buried in the protein, and it is most likely co-ordinated by two helices.

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