Proteins are a diverse and abundant class of biomolecules,constituting more than 50%of the dry weight of cells.This diversity and abundance reflect the central role of proteins in virtually all aspects of cell structure and function.An extraordinary diversity of cellular activity is possible only because of the versatility inherent in proteins,each of which is specifically tailored to its biological role.Proteins are a diverse and abundant class of biomolecules, constituting more than 50% of the dry weight of cells. This diversity and abundance reflect the central role of proteins in virtually all aspects of cell structure and function. An extraordinary diversity of cellular activity is possible only because of the versatility inherent in proteins, each of which is specifically tailored to its biological role