Cerda Haynes, Berta de laDíaz Quintana, Antonio JesúsNavarro Carruesco, José AntonioHervás Morón, ManuelRosa Acosta, Miguel Ángel de la2022-06-082022-06-081999Cerda Haynes, B.d.l., Díaz Quintana, A.J., Navarro Carruesco, J.A., Hervás Morón, M. y Rosa Acosta, M.Á.d.l. (1999). Site-directed Mutagenesis of Cytochromec 6 from Synechocystissp. PCC 6803. Journal of Biological Chemistry, 274 (19), 13292-13297.0021-9258https://hdl.handle.net/11441/134213This paper reports the first site-directed mutagenesis analysis of any cytochrome c 6, a heme protein that performs the same function as the copper-protein plastocyanin in the electron transport chain of photosynthetic organisms. Photosystem I reduction by the mutants of cytochromec 6 from the cyanobacteriumSynechocystis sp. PCC 6803 has been studied by laser flash absorption spectroscopy. Their kinetic efficiency and thermodynamic properties have been compared with those of plastocyanin mutants from the same organism. Such a comparative study reveals that aspartates at positions 70 and 72 in cytochrome c 6 are located in an acidic patch that may be isofunctional with the well known “south-east” patch of plastocyanin. Calculations of surface electrostatic potential distribution in the mutants of cytochromec 6 and plastocyanin indicate that the changes in protein reactivity depend on the surface electrostatic potential pattern rather than on the net charge modification induced by mutagenesis. Phe-64, which is close to the heme group and may be the counterpart of Tyr-83 in plastocyanin, does not appear to be involved in the electron transfer to photosystem I. In contrast, Arg-67, which is at the edge of the cytochrome c 6 acidic area, seems to be crucial for the interaction with the reaction center.application/pdf6 p.engAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/info:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccesshttps://doi.org/10.1074/jbc.274.19.13292