Estimating the number of protein folds and families from complete genome data

Using the data on proteins encoded in complete genomes, combined with a rig orous theory of the sampling process, we estimate the total number of prote in folds and families, as well as the number of folds and families in each genome. The total number of folds in globular, water-soluble proteins is es timated at about 1000, with structural information currently available for about one-third of that number. The sequenced genomes of unicellular organi sms encode from approximately 25%, for the minimal genomes of the Mycoplasm as, to 70-80% for larger genomes, such as Escherichia coli and yeast, of th e total number of folds, The number of protein families with significant se quence conservation was estimated to be between 4000 and 7000, with structu res available for about 20% of these. (C) 2000 Academic Press.