A reconstituted light-harvesting complex from the green sulfur bacterium Chlorobium tepidum containing CsmA and bacteriochlorophyll a.

Abstract:

:Green sulfur bacteria possess two light-harvesting antenna systems, the chlorosome and the Fenna-Matthews-Olson (FMO) protein. In addition to self-aggregated bacteriochlorophyll (BChl) c, chlorosomes of Chlorobium tepidum contain a small amount of BChl a (ratio 100:1). The chlorosomal BChl a is associated with CsmA, a 6.2 kDa protein that accounts for more than 50% of the protein content of chlorosomes. This CsmA-BChl a complex is located in the chlorosome baseplate with the hydrophilic C-terminal part of CsmA in contact with the FMO protein. CsmA was purified from Chl. tepidum. Isolated chlorosomes were lyophilized and extracted with chloroform/methanol (1:1, v/v). The extract was further purified using gel filtration and reverse-phase HPLC and the purity of the preparation confirmed by SDS-PAGE. Mass spectrometric analysis showed an m/z of 6154.8, in agreement with the calculated mass of the csmA gene product after C-terminal processing. CD spectroscopy of the isolated protein showed that the main structural motif was an alpha-helix. We have reconstituted the isolated CsmA protein with BChl a in micelles of n-octyl beta-d-glucopyranoside. The resulting preparation reproduced the spectral characteristics of the CsmA-BChl a complex present in the chlorosome baseplate.

journal_name

Biochemistry

journal_title

Biochemistry

authors

Pedersen MØ,Pham L,Steensgaard DB,Miller M

doi

10.1021/bi701616r

subject

Has Abstract

pub_date

2008-02-05 00:00:00

pages

1435-41

issue

5

eissn

0006-2960

issn

1520-4995

journal_volume

47

pub_type

杂志文章