Other than genes known to function in mobility (insertion sequence, transposase, recombinase and integrase), the mobile elements carry key genes that are important in biological systems of prokaryotic organisms, for instance, those involved in defense systems (Restriction Modification, abortive infection protein), drug resistance (EmrB/QacA subfamily, tetracycline resistance protein, cytochrome P450, cyclase family protein) and response to environmental stress (cold shock protein, heat shock protein). The gene discussed is PROS1; the disease is infection.