Topography of the photosynthetic apparatus of Chloroflexus aurantiacus
The isolation and identification of reaction center, antenna bacteriochlorophyll a (Bchl a), and chlorosome antenna Bchl c polypeptides of Chloroflexus aurantiacus have been described. Subsequently, the localization of the chlorosome- and pigment-specific polypeptides was probed in two subcellular fractions. The reaction center preparation contained a major polypeptide with an apparent molecular weight of 26,000. The antenna Bchl a (B808-866) complex, also a cytoplasmic membrane constituent, was isolated by hydrophobic interaction chromatography on phenyl-Sepharose. In fractions with the highest purity and still native absorption properties, only one polypeptide of M/sub r/ 5300 was found. Purified chlorosomes contained three major proteins (M/sub r/ 18000, 11,000, and 3700), and a fourth polypeptide (M/sub r/ 5800) was present in minor quantities. The M/sub r/ 3700 polypeptide was found to be associated with the antenna Bchl c. The two larger chlorosome proteins were accessible to proteinase K proteolyses and could additionally be modified with the membrane surface specific photolabel 3-azido-2,7-naphthalenedisulfonate. From the resistance against proteolytic cleavage and the lack of photolabeling, it was surmised that the antenna Bchl c polypeptide (M/sub r 3700) is located in the chlorosome interior. Upon chemical cross-linking with dimethyl 3,3'-dithiobis(propionimidate), only dimers of the M/sub r/ 3700 protein were formed in high yield. According to calculations, this dimer was comprised of 2 copies of the M/sub r/ 3700 protein and 10-16 molecules of Bchl c. The cross-linking pattern of the B808-866 antenna Bchl a protein (M/sub r/ 5300) indicated a quaternary structure of a trimer, which should be part of a penta- or hexameric in vivo aggregate.
- Research Organization:
- Univ. of Massachusetts, Amherst
- OSTI ID:
- 6500568
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 23:16; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BIOLOGY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CHLOROPHYLL
CYTOLOGY
CYTOPLASM
DECOMPOSITION
DIMERS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MEMBRANES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDES
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC REACTION CENTERS
PHYTOCHROMES
PIGMENTS
POLYPEPTIDES
PORPHYRINS
PROTEINS
PROTEOLYSIS