Presence of importer-specific domains and co-occurrence between transporters across BGCs. (A) Spearman's correlations between commonly occurring Pfam transporter domains across MIBiG BGCs—only correlations with P < 0.001 are shown. (B) Counts of Pfam transporter substrate binding domain families and corresponding substrate binding protein clusters described by Berntsson et al. (2010). (C) Counts of importer-specific CATH domains across MIBiG BGCs. The CATH functional family “Iron ABC permease” is essentially synonymous with the FecCD Pfam.