The N-terminal rhodanese domain from Azotobacter vinelandii has a stable and folded structure independently of the C-terminal domain

Sulfurtransferase are enzymes involved in the formation, conversion and transport of compounds containing sulfanesulfur atoms. Although the three-dimensional structure of the rhodanese from the nitrogen-fixing bacterium Azotobacter vinelandii is known, the role of its two domains in the protein conformational stability is still obscure. We have evaluated the susceptibility to proteolytic degradation of the two domains of the enzyme. The two domains show different resistance to the endoproteinases and, in particular, the N-terminal domain shows to be more stable to digestion during time than the C-terminal one. Cloning and overexpression of the N-terminal domain of the protein was performed to better understand its functional and structural role. The recombinant N-terminal domain of rhodanese A. vinelandii is soluble in water solution and the spectroscopic studies by circular dichroism and heteronuclear NMR spectroscopy indicate a stable fold of the protein with the expected a=b topology. The results indicate that this N-terminal domain has already got all the elements necessary for an Cterminal domain independent folding. Its solution structure by NMR, actually under course, will be a valid contribution to understand the role of this domain in the folding process of the sulfurtransferase.