Enzyme evolution explained (sort of).

Sites in proteins evolve at markedly different rates; some are highly conserved, others change rapidly. We have developed a maximum likelihood method to identify regions of a protein that evolve rapidly or slowly relative to the remaining structure. We also show that solvent accessibility and distance from the catalytic site are major determinants of evolutionary rate in eubacterial isocitrate dehydrogenases. These two variables account for most of the rate heterogeneity not ascribable to stochastic effects.