Distribution of protein isoelectric point in halophilic and non-halophilic organisms predicted from genome sequences (adapted from ref. 13). The percent of all predicted proteins is plotted versus their calculated isoelectric points. The distribution of protein isoelectric points for the halophile Halobacterium sp. NRC-1 (red) is skewed towards acidic range while those of non-halophiles (black) have a broader distribution of isoelectric points with an average of neutrality in most cases.