Comparison of arrangement of the smo, mmo, and bmo genes. The predicted monooxygenase subunits of Smo are as follows: SmoX, α-hydroxylase; SmoY, β-hydroxylase; SmoB1, coupling/effector protein; SmoC1, γ-hydroxylase; and SmoZ, reductase. The level of predicted amino acid identity between three of the hydroxylase subunits is indicated in the boxes between the open reading frames.