Fig. 11From: The Origin and Evolution of Metabolic Pathways: Why and How did Primordial Cells Construct Metabolic Routes?Evolutionary model proposed for the origin and evolution of hisA and hisF (b). The first and the second quarters and two single (β/α) modules of the HisA protein from Thermotoga maritima are reported in (a) and (c), respectivelyBack to article page