Structure of the crystalline complex of cytidylic acid (2'-CMP) with ribonuclease at 1.6 Å resolution. Conservation of solvent sites in RNase-A high-resolution structures

The X-ray structure of the inhibitor complex of bovine ribonuclease A with cytidylic acid (2'-CMP) has been determined at 1.6 Å resolution and refined by restrained least squares to R = 0.17 for 11 945 reflections. Binding of the inhibitor molecule to the protein is confirmed to be in the productive mode associated with enzyme activity. A study of conserved solvent sites amongst high-resolution structures in the same crystal form reveals a stabilizing water cluster between the N and C termini.