Site-specific amino acid frequency, fitness and the mutational landscape model of adaptation in human immunodeficiency virus type 1

Abstract

Analysis of the intensely studied HIV-1 gp120 V3 protein region reveals that the among-population mean site-specific frequency of an amino acid is a measure of its relative marginal fitness. This surprising result may arise if populations are displaced from mutation-selection equilibrium by fluctuating selection and if the probability of fixation of a beneficial amino acid is proportional to its selection coefficient. Copyright © 2006 by the Genetics Society of America.