NMR backbone assignment. (A) [1H, 15N] spectrum of the uniformly 15N,13C labeled PFV RNase H-(Q591-N751). Numbers refer to amino acid positions of the corresponding residues in the full length PFV PR-RT. NH2 side chains are connected by lines, the tryptophan side chains are marked by 'sc'. Several amino acids of the C-helix are marked by boxes. (B) Secondary chemical shift indices for H
, CO nuclei, and the consensus of PFV RNase H-(Q591-N751). Deduced β-strands are represented by arrows, and helical regions by cylinders. Precise amino acid numbering of the secondary structure elements is given in the text.