Earth’s atmosphere changes over time – the amount of oxygen has built up from virtually zero over billions of years. Living organisms have had to adapt to this changing atmosphere, developing mechanisms to cope with the presence of oxygen and the dangerous by-products of respiration known as reactive oxygen species (ROS), which can damage our cells. Proteins and enzymes are particularly susceptible to this oxidative damage, which can lead to many conditions including Alzheimer's, cancer and heart failure. Studying the protein structural database has revealed that many protein structures contain the amino acids tyrosine and tryptophan. Researchers believe that these amino acids are being used to transport ROS away from the vulnerable sites of proteins. Pictured is SOD2, an antioxidant enzyme involved with respiration. The red, pink and blue chains represent different tyrosines and tryptophans. This finding gives insight into how cells adapt to protect against unwanted oxygen species.
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