The Thermotoga maritima gene is located within a cluster of genes that are homologous to genes whose translated products are involved in xylulose metabolism. In E. coli, the catabolism of endogenously formed xylulose is mediated by IclR family member YiaJ. The crystal structure of the TM0065 protein, also known as TM-IclR, was resolved at 2.2 Å [95]. The protein consists of two α/β domains, a small N-terminal DNA-binding domain, and a large C-terminal putative signal-binding domain. These domains are linked by an α-helix and a short loop. The protein crystallized as a dimer and the dimerization interface comprises the α-helices H1 and H4.
The sequences of IclR proteins can be subdivided into 5 major orthologous subgroups. However, the five 3D structures currently available on IclR proteins all group in one of these subgroups. To elucidate whether members of all IclR subgroups share a similar sequence of secondary structure elements, a representative of all subgroups was selected on the basis that the function is known and that no 3D structural information is available. The only IclR sequence from an archaebacterium has also been included in this analysis. The result is shown in this figure:
