Hur proteiner kan utvecklas att göra nya saker utan att tappa de gamla

This can be understood through a broader consideration of protein structure and function. Enzymes catalyze reactions in large part due to their structures, which include binding domains for different biomolecules. These binding domains evolve specificity for particular target molecules, so that they have a lock-and-key configuration. But the system is not a perfect one-key-fits-one-lock arrangement. Instead, an enzyme may catalyze additional reactions inefficiently, over and above the one it has been adapted to catalyze well. Small changes in the amino acid sequence can sometimes add significantly to the efficiency in catalyzing these other reactions, without detracting from the primary adaptation.