REDOX PROPERTIES ARE CONSERVED IN RUBISCOS FROM DIATOMS AND GREEN ALGAE THROUGH A DIFFERENT PATTERN OF CYSTEINES1

Authors

  • Julia Marín-Navarro,

    1. Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de València, E46100-Burjassot, Valencia, Spain
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    • 2

      Both authors contributed equally to this work.

    • 3

      Present address: Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas, Apdo. de Correos 73, Burjassot, Valencia E46100, Spain.

  • Maria Jesús García-Murria,

    1. Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de València, E46100-Burjassot, Valencia, Spain
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    • 2

      Both authors contributed equally to this work.

    • 4

      Present address: Centro de Investigación Principe Felipe, Avda. Autopista del Saler, 16, E46012 Valencia, España.

  • Joaquín Moreno

    1. Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de València, E46100-Burjassot, Valencia, Spain
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  • 1

    Received 5 March 2009. Accepted 18 November 2009.

Abstract

Eukaryotic RUBISCO appears in two sequence-diverging forms, known as red-like (present in nongreen algae) and green-like (of green algae and higher plants) types. Oxidation of cysteines from green-like RUBISCOs is known to result in conformational changes that inactivate the enzyme and render a relaxed structure more prone to proteolytic attack. These changes may have regulatory value for green algae and higher plants, promoting RUBISCO catabolism under stress conditions. We compare here red-like RUBISCOs from several diatoms with a representative green-like RUBISCO from Chlamydomonas reinhardtii, paying special attention to the cysteine-dependent redox properties. Purified diatom RUBISCO preparations displayed a specific carboxylase activity about one order of magnitude lower than that of the C. reinhardtii P. A. Dang. enzyme. Despite having different patterns of cysteine residues in their primary sequence, the red-like enzymes from diatoms inactivated also through oxidation of cysteine sulfhydryls to disulfides with a transition midpoint identical to that of the green-like forms. Cysteine oxidation resulted also in structural modifications of the diatom RUBISCOs, as recognized by a higher sensitivity of the oxidized enzyme to in vitro proteolysis. The coincident redox properties of red- and green-like RUBISCO types suggest that these changes are part of a physiologically significant regulatory mechanism that has been convergently implemented in both groups with a different set of cysteine residues.

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