Electron transport chain history

The history of the Cyt b c complex itself may be closely related to that of the reaction centers. The occurrence of such a complex in photosynthetic and respiratory electron transport chains of chloroplasts, mitochondria and eubacteria sug-... 

To diminish these threats, nature has created a family of metalloenzymes, the SODs. They catalyze the dismutation of superoxide to dioxygen and hydrogen peroxide (Eqs. (1) and (2)). They are differentiated by the redox-active metal copper (Cu/Zn SOD), manganese (MnSOD), iron (FeSOD), or nickel (NiSOD) superoxide dismutases and fall into three evolutionary families (Fig. 2) (10). The iron and manganese SODs are structurally similar and are found in prokaryotes and in the matrix of mitochondria (near the electron transport chain), respectively. Nickel containing SODs are known in some prokaryotes, whereas Cu/Zn are present in the cytosols of virtually all eukaryotic cells and have an independent evolutionary history. 

Iron and sulfur can be extracted from F. the resulting apoferredoxin is reactivated by iron(II) salts and sulfides. The synthesis of the iron-free protein has been achieved by the Merrifield technique. On account of their properties as redox systems (Fe +e" Fe ") the F. effect electron transport between enzyme systems but do not exhibit any enzymatic activity. They transport electrons in the respiratory chain, in photosynthesis, and in nitrogen fixation. The iron-sulfur protein P439 of the Fc4S4-type (Mr 11600) plays a role in photosynthesis. Conclusions can be drawn about the evolutionary histories of plants from the similarities and differences in the amino acid sequences. For the evolutionary history of F. in photosynthesis, see Lit.K F. with FejSj- and FejSg-clusters also occur in bacteria Lit. TrendsBiochem.Sci. 13,30-33(1988). FEMSMicrobiol. Rev. 54,155-176 (1988) Trends Biochem. Sci. 13,369 f. (1988). 

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