PROSITE documentation PDOC00748
Antenna complexes alpha and beta subunits signatures


In photosynthetic bacteria the antenna complexes function as light-harvesting systems that absorb light radiation and transfer the excitation energy to the reaction centers. The antenna complexes are generally composed of two polypeptides (α and β chains); two or three bacteriochlorophyll (BChl) molecules and some carotenoids [1,2].

Both the α and the β chains of antenna complexes are small proteins of 42 to 68 residues which share a three-domain organization. They are composed of a N-terminal hydrophilic cytoplasmic domain followed by a transmembrane region and a C-terminal hydrophilic periplasmic domain. In the transmembrane region of both chains there is a conserved histidine which is most probably involved in the binding of the magnesium atom of a bacteriochlorophyll group. The β chains contain an additional conserved histidine which is located at the C-terminal extremity of the cytoplasmic domain and which is also thought to be involved in bacteriochlorophyll-binding.

We have developed signature patterns for the α and for the β subunits. These signature patterns include the conserved histidine residues.

Last update:

December 2004 / Pattern and text revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

ANTENNA_COMP_ALPHA, PS00968; Antenna complexes alpha subunits signature  (PATTERN)

ANTENNA_COMP_BETA, PS00969; Antenna complexes beta subunits signature  (PATTERN)


1AuthorsWagner-Huber R. Brunisholz R.A. Bissig I. Frank G. Suter F. Zuber H.
SourceEur. J. Biochem. 205:917-925(1992).

2AuthorsBrunisholz R.A. Zuber H.
TitleStructure, function and organization of antenna polypeptides and antenna complexes from the three families of Rhodospirillaneae.
SourceJ. Photochem. Photobiol. B 15:113-140(1992).
PubMed ID1460542

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