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Original - "bacterial antenna complex"

Bacterial antenna complex proteins are the main light-absorbing components in photosynthetic bacteria.

In photosynthetic purple bacteria the antenna complexes function as light-harvesting systems that absorb light radiation and transfer the excitation energy to the photosynthetic reaction centres. The antenna complexes are generally composed of two types of polypeptides (alpha and beta chains) which are arranged in a ring-like fashion creating a cylinder that spans the membrane; the proteins bind two or three types of bacteriochlorophyll (BChl) molecules and different types of carotenoids depending on the species. Both the alpha and the beta 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 beta 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.

Edit - "bacterial antenna complex"

Note: Sources 4 to 8 were used for the edits. 272 words added. In the edit, source 4 was added to paragraph 3, sentence one, just as an additional supporting source for the existing information. The 2 paragraphs under "original" above were the only 2 paragraphs in the original article.

INTRODUCTION: Bacterial antenna complex proteins are the main light-absorbing components in photosynthetic bacteria. Also known as a light-harvesting complex/system, the bacterial antenna complex is responsible for the transfer of solar energy to the photosynthetic reaction centre.

The bacterial antenna complexes of all photosynthetic bacteria have similar features. They consist of light-absorbing pigments that are either non-covalently associated with integral proteins in the case of purple photosynthetic bacteria and cyanobacteria, or present in chlorosomes in the case of green photosynthetic bacteria. The light-absorbing pigments in chlorosomes do not associate with integral proteins for assembly. Green and purple photosynthetic bacteria utilize different bacteriochlorophyll molecules while cyanobacteria contain chlorophyll, the light-absorbing pigments found in plants. Purple photosynthetic bacteria, particularly Rhodopseudomonos acidophilia of purple non-sulfur bacteria, have been one of the main groups of organisms used to study bacterial antenna complexes so much is known about this group's photosynthetic components.

Bacterial Antenna Complexes of Purple Photosynthetic Bacteria
In photosynthetic purple bacteria there are usually two antenna complexes that are generally composed of two types of polypeptides (alpha and beta chains). These proteins are arranged in a ring-like fashion creating a cylinder that spans the membrane; the proteins bind two or three types of bacteriochlorophyll (BChl) molecules and different types of carotenoids depending on the species. LH2 is the outer antenna complex that spans the membrane. It is peripheral to LH1, an antenna complex (also known as the core antenna complex) that is directly associated with the reaction centre. Unlike for LH1 complexes, the amount of LH2 complexes present vary with growth conditions and light intensity.

Both the alpha and the beta 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 beta 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.

The particular chemical environment of the Bchl molecules influences the wavelength of light they are able to absorb. LH2 complexes of R. acidophils have BChl a molecules that absorb at 850nm and 800nm respectively. BChl a molecules that absorb at 850nm are present in a hydrophobic environment. These pigments are in contact with a number of non-polar, hydrophobic residues. BChl a molecules that absorb at 800nm are present in a relatively polar environment. The formulated N-terminus of the alpha polypeptide, a nearby histidine, and a water molecule are responsible for this.

Bacterial Antenna Complexes of Green Photosynthetic Bacteria
See chlorosomes.

Bacterial Antenna Complexes of Cyanobacteria
See cyanobacteria. Grewalharvir (talk) 05:53, 9 October 2017 (UTC)