TABLE 2.
Residues implicated in activity and metal binding by structural studies of nucleasesa
| Vhs residue | Corresponding residue in:
|
|||
|---|---|---|---|---|
| T5 5′ exonuclease (10, 11) | Taq I DNA polymerase (10, 33) | T4 RNase H (10, 44) | Human FEN-1 (10, 28, 29) | |
| D34 | D26 (Mn-1) | D18 (M-1) | D19 (Mg-1) | |
| D82 | D71 (Mg-1) | |||
| K96 | ||||
| E192 | E128 (Mn-1) | E117 (M-3) | ||
| D194 | D119 (M-1, M-3) | D132 (Mg-1, M-2) | ||
| D195 | E131 (Mn-1) | D120 (M-3) | ||
| T211 | S153↔D19 | |||
| D213 | D153 (Mn-1, Mn-2) | D142 (M-1, M-2) | D155 (Mg-1) | |
| D215 | D155 (Mn-2) | D144 (M-2) | D157 (Mg-2) | D181 (Mg-2) |
| D261 | D204 (Mn-2) | D200 (Mg-2) | ||
Key conserved residues of the Vhs polypeptide are shown in column 1. The corresponding residues of cellular and phage nucleases are shown in columns 2 through 5. T5 5′ exonuclease and T4 RNase H have been shown to bind two manganese (Mn-1 and Mn-2) and two magnesium (Mg-1 and Mg-2) ions, respectively. Human FEN-1 has been shown to bind two magnesium ions, while Taq I DNA polymerase binds three metal ions (M-1, M-2, and M-3). Residues that have been shown in structural studies to play key roles in metal binding are indicated for the different nucleases. S153 and D19 of T4 RNase H have been shown to interact by hydrogen bonding. Data are from the references listed at the top of each column.