The structural basis of molecular adaptation

The study of molecular adaptation has long been fraught with difficulties,not the least of which is identifying out of hundreds of amino acidreplacements those few directly responsible for major adaptations. Sixstudies are used to illustrate how phylogenies, site- directed mutagenesis,and a knowledge of protein structure combine to provide much deeperinsights into the adaptive process than has hitherto been possible. Ancientgenes can be reconstructed, and the phenotypes can be compared to modernproteins. Out of hundreds of amino acid replacements accumulated overbillions of years those few responsible for discriminating betweenalternative substrates are identified. An amino acid replacement of modesteffect at the molecular level causes a dramatic expansion in an ecologicalniche. These and other topics are creating the emerging field of"paleomolecular biochemistry."