A unique family of proteins have been identified in the Deinococcus genus with an N-terminal cobalarnin (vitamin 1312) chelatase domain denoted CbiX and an additional unique C-terminal domain with unknown function. Here we report the first crystal structure from this new family of proteins with the structure of Deinococcus radiodurans protein DR2241. The structure reveals a multi-domain protein where domains A (residues 1-132) has the same fold as the small CbiX (CbiXs), domains A and B (residues 1-272) follow the chelatase super-family fold and the two additional unique domains C and D have no structural homologues. Domain D harbours the sequence motifs CxxC and CxxxC, in which DR2241 gives the first evidence that these motifs bind a [4Fe-4S) iron-sulphur cluster. In solution there are indications of multimeric forms, and in the crystallographic asymmetric unit a tetramer is found where domains C and D are involved in stabilising the tetrameric assembly. (c) 2007 Published by Elsevier Inc.