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Sulfur is a functionally important element of living matter. Rhodanese is involved in the enzymatic production of the sulfane sulfur which has been suggested as the biological relevant active sulfur species. Rhodanese domains are ubiquitous structural modules occurring in the three major evolutionary phyla. | ễFEBS Journal A new sulfurtransferase from the hyperthermophilic bacterium Aquifex aeolicus Being single is not so simple when temperature gets high Marie-Cecile Giuliani1 Pascale Tron1 Gisele Leroy1 Corinne Aubert1 Patrick Tauc2 and Marie-Therese Giudici-Orticoni1 1 Laboratoire de Bioénergétique et Ingenierie des Proteines BIP IBSM-CNRS Marseille France 2 Laboratoire de Biotechnologie et de Pharmacologie Genetique Appliquee - ENS-CACHAN Cachan France Keywords Aquifex aeolicus hyperthermophile oligomerization sulfurtranferase thermostability Correspondence M.-T. Giudici-Orticoni Laboratoire de Bioenergetique et Ingenierie des Proteines IBSM-CNRS 31 chemin Joseph Aiguier 13402 Marseille cedex 20 France Fax 33 4 91 16 45 78 Tel 33 4 91 16 45 50 E-mail giudici@ibsm.cnrs-mrs.fr Received 20 April2007 revised 6 July 2007 accepted 12 July 2007 doi 10.1111 j.1742-4658.2007.05985.x Sulfur is a functionally important element of living matter. Rhodanese is involved in the enzymatic production of the sulfane sulfur which has been suggested as the biological relevant active sulfur species. Rhodanese domains are ubiquitous structural modules occurring in the three major evolutionary phyla. We characterized a new single-domain rhodanese with a thiosulfate cyanide transferase activity Aq-477. Aq-477 can also use tetrathionate and polysulfide. Thermoactivity and thermostability studies show that in solution Aquifex sulfurtranferase exists in equilibrium between monomers dimers and tetramers shifting to the tetrameric state in the presence of substrate. We show that oligomerization is important for thermostability and thermoactivity. This is the first characterization of a sulfurtransferase from a hyperthermophilic bacterium which moreover presents a tetrameric organization. Oligomeric Aq-477 may have been selected in hyperthermophiles because subunit association provides extra stabilization. Sulfur adds considerable functionality to a wide variety of biomolecules because of its .
