CO-INERTIA ANALYSIS OF AMINO-ACID PHYSICOCHEMICAL PROPERTIES AND PROTEIN-COMPOSITION WITH THE ADE PACKAGE

A multivariate analysis method called co-inertia analysis was used to determine the main relationships between two data tables having identi cal rows. This method is available in the ADE multivariate analysis pa ckage for Macintosh micro-computers. It was applied to two data sets, one containing the amino-acid composition of 999 E. coli proteins, and the other the values of 402 physico-chemical properties for the 20 na tural amino-acids. There were strong relationships between amino-acid physico-chemical properties and the composition of proteins. The first common factor was hydrophobicity, it is linked to the biological envi ronment of proteins, either in the cytoplasm (or outside the cell), or in the nonpolar environment of the phospholipid bilayer of biological membranes. The second factor linked the expressivity of protein genes and the propensity of amino-acids to form alpha helix/beta sheets. Th e third factor showed that heavy, aromatic amino-acids tend to be avoi ded, except when they are needed for structural or functional reasons. These results are discussed in terms of selective pressure acting on amino-acid composition of proteins.