Abstract
A number of surface residues of cytochrome c(6) from the cyanobacterium Anabaena sp. PCC 7119 have been modified by site-directed mutagenesis. Changes were made in six amino acids, two near the heme group (Val-25 and Lys-29) and four in the positively charged patch (Lys-62, Arg-64, Lys-66, and Asp-72). The reactivity of mutants toward the membrane-anchored complex photosystem I was analyzed by laser flash absorption spectroscopy. The experimental results indicate that cytochrome c(6) possesses two areas involved in the redox interaction with photosystem I: 1) a positively charged patch that may drive its electrostatic attractive movement toward photosystem I to form a transient complex and 2) a hydrophobic region at the edge of the heme pocket that may provide the contact surface for the transfer of electrons to P(700). The isofunctionality of these two areas with those found in plastocyanin (which acts as an alternative electron carrier playing the same role as cytochrome c(6)) are evident.
Highlights
A number of surface residues of cytochrome c6 from the cyanobacterium Anabaena sp
The experimental results indicate that cytochrome c6 possesses two areas involved in the redox interaction with photosystem I: 1) a positively charged patch that may drive its electrostatic attractive movement toward photosystem I to form a transient complex and 2) a hydrophobic region at the edge of the heme pocket that may provide the contact surface for the transfer of electrons to P700
The isofunctionality of these two areas with those found in plastocyanin are evident
Summary
A number of surface residues of cytochrome c6 from the cyanobacterium Anabaena sp. PCC 7119 have been modified by site-directed mutagenesis. The experimental results indicate that cytochrome c6 possesses two areas involved in the redox interaction with photosystem I: 1) a positively charged patch that may drive its electrostatic attractive movement toward photosystem I to form a transient complex and 2) a hydrophobic region at the edge of the heme pocket that may provide the contact surface for the transfer of electrons to P700. The isofunctionality of these two areas with those found in plastocyanin (which acts as an alternative electron carrier playing the same role as cytochrome c6) are evident. Arg-67, which is located at the edge of the Cyt c6 acidic area, seems to be crucial
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