High degree of homology of the deduced protein structures of the tetracycline-resistance determinants between Bacillus subtilis plasmid pNS1981 and Staphylococcus aureus plasmid pTP5

The amino acid sequences of the tetracycline-resistance (Tcr) determinants of Bacillus subtilis plasmid pNS1981 and Staphylococcus aureus plasmid pTP5 have been deduced from their nucleotide sequences and compared. The deduced Tcr proteins (TETs) of pNS1981 (458 amino acids) and pTP5 (459 amino acids) show a considerable homology (60% identical). If homologous amino acid replacement is taken into account, the homology becomes 80%. Both TET proteins are highly hydrophobic, as expected for a membrane-binding protein, and their polarities are calculated at 32–33%. The putative secondary structures of both TET proteins have been also shown to be significantly homologous, being abundant in β-sheets. The predicted positions of β-sheets show a nice coincidence between both TET proteins. α-Helix has a tendency to be formed at nonhomologous regions of the primary structures between both TET proteins. However, the predicted positions of α-helices coincide in a frequency greater than 50%. α-Helix and random coil moderately occur at the hydrophilic regions in both TET proteins.