Function of protein families

In inter mediary metabolism and nucleic acid metabolism account foe about 15% of the proteins represented in top proteome. Protein associated with structure and protein synthesis ,Another way to look at the proteome is to divide it in to families of proteins that carry out related functions. For example. Some proteins serve structural role some are participants in signaling pathways and other handle essential metabolic chores such as nucleic acid synthesis or carbohydrate catabolism. Based on classification by domain content and associated functional roles, Venter and colleagues estimated that division of protein functions in proteins encoded by the human genome
Enzymes involved in inter mediary metabolism and turn over (cytoskeleton proteins, ribosomal protein, chaperones, and mediators of protein degradation) account collectively for another 15%-20%. Another 20% - 35% consist of signaling proteins and DNA binding proteins. Although these numbers offer a useful perspective on how the genome is divided by protein functions, they do not tell us how much of any protein or protein class is expressed at any given time in a cell. Approximately 40% of the genome encodes protein products with on know n function. Assigning functions to these gene products represents the most fundamental challenge for human functional genomics.
Complete genomic sequences of several organisms have been completed and these data have allowed analysts to predict the products of all the organism’s genes. Moreover, based on the predicted amino acid sequences of each gene product these proteins have been classified on the basis of the domains and sequence motifs they contain.