Proteins bind with one or more metal ions in their native state to facilitate the biological function of the protein. The study of critical interactions between the biological molecules and metals is an important field of study. In this work, we focus on the functional specificity of residues coordinating with the metals commonly found in β-lactamases, Zn, Mg, Na, Cu, Mn, Ni, Fe, K, and Cd through non-classical interactions. All the residues located in the metal-binding site of β-lactamases are involved in non-classical interactions. The data obtained from this study will be useful to understand the functional role of metal-coordinating residues in the specificity of β-lactamases, thus offering promising strategy to design effective β-lactamase inhibitors. © 2014 Taylor & Francis.