Abstact

The structure of a catalytically inactive RNase-related protein from Calystegia sepium (CalsepRRP) has been resolved by protein crystallography at a resolution of 2.05 A and an R factor of 20.74%. Although the protein is completely devoid of ribonuclease activity, it adopts the typical alpha + beta structure of non-base-specific RNases. Analysis of the structure revealed that two amino-acid substitutions in the 'active' P1 site, in combination with the less hydrophobic/aromatic character of the B1 base-recognition site and a completely disrupted B2 base-recognition site, might account for this complete lack of activity.