In: Biology
There seems to be some constraint on protein size (50-400 a.a.). Why is this?
Finding the best fit of protein length distributions to well characterized mathematical models can offer insights about evolutionary trends, selective pressures and constraints for protein function and structure. Since protein stability is determined in part by length, the size of proteins has a selective advantage and therefore, influences the evolution of proteomes in each lineage. One could assume that proteins smaller than 130 aa are less functional or less stable than proteins larger than 200 aa. Indeed, the need to explain the origin of large proteins was one of the major reasons for invoking gene or exon duplication in the starter-set hypothesis. If size distributions can be explained by a simple stochastic model without assuming massive gene or exon duplication; then, the random-origin hypothesis would be supported. If the same model applies for all species, one could also hypothesize that protein size has increased by the same evolutionary process that caused bacterial proteins to be larger than archaeal proteins.