Fig 2. Plot of denaturation temperature versus environmental temperature including modern thioredoxins (red), resurrected ancestral thioredoxins (blue) and resurrected ancestral elongation factors (yellow).
Elongation factor data conform approximately to the continuous line representing Tm = TENV. Modern and ancestral thioredoxins describe a general trend that conforms a common linear dependence at about 50 degrees above the Tm = TENV line (the continuous line described by the equation Tm = TENV+50 is meant to guide the eye to this common dependence). Environmental temperatures for resurrected proteins are calculated as the ancestral ocean temperatures derived from the isotopic composition of cherts (see Fig 1). Only resurrected proteins for which this calculation is possible are shown. Environmental temperatures for modern thioredoxins are the published values of the corresponding organismal growth temperatures (or the midpoints of an optimal growth range when this is provided). See "Materials and Methods" for further details on the source of the thioredoxin data in this figure. Elongation factor data are taken from [10].