Contact-based and sequence-based analyses of protein evolutionary groups are expected to be complementary and to some extend concordant. One such way to compare the similarity of two proteins at the sequence level is to calculate their percentage identity, or what fraction of amino acids in an aligned sequence are identical. The percentage identity matrix (PIM) for all ßlactamases studied is shown in Figure . As a means of comparison, we also generated a protein contact similarity matrix (PCSM) based on contact networks (Figure ), with the metric the ratio of conserved contacts against non-conserved contacts between any two proteins. The Spearman rank order correlation between the PIM and PCSM matrices is 0.71. This indicates relatively strong concordance between evolutionary conservation of key interaction networks and sequence conservation across class A β-lactamases.