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Genetic experiments in bacteria have shown the suf operon is involved in iron homeostasis and the oxidative stress response. The sufB and sufC genes that always occur together in bacteria are also found in plants, and even the malaria parasite, associated with the plastid organelle. Although the suf operon is believed to encode an iron-dependent ABC-transporter there is no direct evidence. By immunolocalization we show here that SufB and SufC are associated with the membrane of Escherichia coli. We also present kinetic studies with a recombinant version of SufC from Thermotoga maritima that shows it is an ATPase and that it interacts with SufB in vitro.

We present a model for the three-dimensional structure of the glutamate-specific endopeptidase from Streptomyces griseus based on the crystal structures of other bacterial proteases of the trypsin family. For the first time a structural model is described which attempts to explain the basis of P1 glutamate specificity in serine proteases. Several important changes to the S1 pocket with respect to other members of the family of different specificity are described. Of particular interest is the presence of a histidine at position 213 and the substitution of Arg-138 by lysine. Other biochemical evidence concerning substrate preferences can be rationalized on the basis of the model.

Organ specific autoimmune diseases are relatively common immunological disorders in man which include thyroid autoimmune disease, insulin-dependent diabetes mellitus and myasthenia gravis. The target autoantigens in some of these diseases have recently been characterised. In thyroid autoimmune disease this includes the key enzyme, thyroid peroxidase (TPO), which is involved in the generation of thyroid hormone. Structural knowledge about autoantigens such as thyroid peroxidase will allow a greater understanding of the interaction between autoantigens and the aberrant immune response, and facilitate the development of strategies for antigen-specific therapeutic manipulation. We report here a prediction of the secondary structure of thyroid peroxidase, together with the results of circular dichroic spectroscopy of a homologous purified enzyme. A combination of 3 secondary structure prediction programs has been used, following multiple sequence alignment, and TPO has been found to consist mainly of alpha-helical conformation, with little beta-sheet present. This structure prediction, together with knowledge of the exon-intron boundaries allows a model for the domain organisation of the TPO molecule to be proposed.