Histidine residues photosynthetic

In photosynthetic bacteria, the four histidine residues coordinated to the iron atom are supplemented by a bidendate ligand. However, a corresponding glutamyl residue is not present in the D2 protein. Michel and Deisenhofer reasoned that since the D- and E-helices in Dl and D2 are of equal length, it is rather... 

Ikezaki and Nakamura have prepared a number of mono(imidazole)-ligated complexes of perchloro(meso-tetramesitylporphyrinato)iron(III), which they view as models for cytochromes c, a class of heme proteins found in photosynthetic, denitrifying, and nitrogen fixing bacteria, in which the heme iron is pentacoordinated with a solvent-exposed histidine residue as the fifth ligand. The spin states were all quantum mechanical admixtures of (S = 5/2, 3/2) as determined by H and NMR, ESR, and solution magnetic moments. 

The hydropathy plot of the 20 kDa protein predicts that it possess two membrane spanning regions (Fig. 2). Each of these membrane spans contain a histidine residue which is part of an consensus amino acid sequence (Ala-X-X-X-His) believed to be involved in the coordination of chlorophyll in photosynthetic bacteria (8). 

Plastocyanin, a copper-containing protein found in photosynthetic systems, is involved in electron transport, with the copper ion switching between the +1 and +2 oxidation states. The copper ion is coordinated with two histidine residues, a cysteine residue, and... 

Fig. 3. Amino-acid sequences of the a- and p-poiypeptides of the core (B870, B1015) and peripherai (B800-850) antenna complexes of purple photosynthetic bacteria. The two polar domains at the N- and C-termini are separated by thin, dashed lines from the middle hydrophobic domain. [1] and [2] mark the conserved histidines and [3] marks the conserved alanine residues.

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