This model represents a small family of proteins homologous (and likely functionally equivalent to) aconitase 1. Members are found, so far in the anaerobe Clostridium acetobutylicum, in the microaerophilic, early-branching bacterium Aquifex aeolicus, and in the halophilic archaeon Halobacterium sp. NRC-1. No member is experimentally characterized. [Energy metabolism, TCA cycle]