Comparison of the amino acid distribution in the proteomes (predicted proteins) of P. falciparum, Homo sapiens, Saccharomyces cerevisiae and Arabidopsis thaliana (5334, 32035, 6699 and 27857 sequences, respectively). Amino acids are grouped with respect to the structural classes defined previously in . The first class defines strong hydrophobic amino acids (V, I, L, F, M, Y, W), that display a similar propensity for yielding regular secondary structures (α-helices and β-strands. The third class includes coil-forming amino acids (G, P, D, N, S), whereas the intermediate class (A, R, C, Q, T, E, K) contains amino acids for which coil and secondary structure forming propensities are similar. The total class I amino acid content is similar in Plasmodium falciparum with respect to other proteomes (see comments in the discussion section). The frequency of cysteine, which is also a frequent component of hydrophobic cores, does not differ in Plasmodium falciparum relatively to other organisms. One can also observe a stable frequency for histidine, which has always a remarkably neutral behavior in the secondary structure propensities.