Studies on the relationships between the synonymous codon usage and protein secondary structural units

The relationship between the synonymous codon usage and protein secondary structural elements (alpha helices and beta sheets) were reinvestigated by taking structural information of proteins from Protein Data Bank (PDB) and their corresponding mRNA sequences from GenBank for four different organisms E. coli, B. subtilis, S. cerevisiae, and Home sapiens. It was observed that synonymous codon families have nonrandom codon usage, but there does not exist any species invariant universal correlation between the synonymous codon usage and protein secondary structural elements. The secondary structural units of proteins can be distinguished from the occurrences of bases at the second codon position. (C) 2000 Academic Press.