Sequence alignment of different RNase H domains. The RNases H from human origin, E. coli, MoMLV RT and HIV-1 RT are shown in comparison to the PFV RNase H. The numbers represent the amino acid numbers of the corresponding full length enzymes. The alignment was performed with the program CLC Protein Workbench 5 (version 126.96.36.199). Arrows below in pink indicate the β-strands in MoMLV RNase H, the corresponding amino acids in the other RNases H are highlighted by pink letters. Blue bars indicate α-helices in MoMLV RNase H, α-helical stretches of the other RNases H are highlighted by blue letters. The C-helices are highlighted by bright cyan boxes. The active site residues are highlighted in yellow.