Figure 6.

Proposed models for the HLH–FdM. (A) molscript model of a possible structure for the HLH–FdM with a pair of [4Fe–4S] clusters bound between parallel HLH. (B) Molecular model of a possible structure for the HLH–FdM with a pair of [4Fe–4S] clusters bound between a pair of antiparallel-oriented, HLH peptides. The distance between the two [4Fe–4S] clusters is in the range of 7–15 Å. (C) Computer model of a possible structure for the HLH–FdM with a single [4Fe–4S] cluster bound between a pair of parallel HLH–FdM peptides. The absence of paramagnetic interaction between the iron–sulfur clusters in HLH–FdM suggests that the model in A in unlikely.