Crystallographic and biochemical studies on dissimilatory sulfite reductases

Thesis dissertation presented to obtain a PhD degree in Biochemistry at Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

Life on earth is only possible through tightly interwoven material transformations through various cycles. Carbon, nitrogen, fosforous and sulfur, with a special interest in the latter, are essential components of all living organisms and represent the most important elements circulating within the biosphere. During this circulation, sulfur can be found in various oxidation states with transformations occurring both biological and chemically. Dissimilatory sulfate reduction is one of those reactions, where sulfate is reduced to the final product sulfide in order to obtain energy for their metabolism. Sulfate reduction however, is not a favourable energetic reaction, and so sulfate is initially activated to adenosine-5’-phosphosulfate (APS) by ATP sulfurylase. APS is then reduced to sulfite by APS reductase allowing the sulfite reductase to reduce sulfite to the final product sulfide in a six electron transfer reaction. This last step can occur in an assimilatory or dissimilatory way.(...)

Finantial support for this work was provided by a Fellowship (SFRH/BD/29519/2006) from Fundação para a Ciência e Tecnologia, and partial support was also provided by Dr. Amir Khan at Trinity College Dublin