Proteins of Thermus thermophilus are resistant to glycation-induced protein precipitation: An evolutionary adaptation to life at extreme temperatures?

In thermophilic bacteria, formation of Maillard products may occur at increased rates because this reaction is favored at higher temperatures. Therefore, specific protective mechanisms against glycation-induced protein precipitation are likely to exist in thermophilic bacteria. Indeed, Thermus thermophilus proteins remained soluble when a cell-free extract of T, thermophilus was incubated at 37°C in the presence of glucose, fructose, or methylglyoxal; whereas E. coli proteins precipitated. In E. coli cell-free extracts, sugar-induced precipitation was accelerated by the addition of 5 μM Fe²⁺ and inhibited by metal chelators, suggesting that glycoxidation processes are involved in the formation of the precipitate. A low lysine content, endogenous small scavenger molecules, or enzymatic " antiglycation" mechanisms for the degradation of AGEs or their precursors could be excluded as possible causes for the resistance to protein precipitation in T. thermophilus. Therefore, the resistance to glycation-mediated protein precipitation is an endogenous property of thermophilic proteins that was acquired during evolution in environments with high glycation activity.