Distributions of transporter classes in biosynthetic gene clusters. (A) Structures of characterized examples of major transporter classes often found in BGCs, colored and labeled by Pfam domains. The extracellular/periplasmic side of the membrane is shown as a red line, and the intracellular side is in blue. (B) The frequencies of common Pfam transporter domains across the bacterial BGCs in the MIBiG database. (C) The percentages of bacterial BGCs in MIBiG that do and do not contain transporter domains. Each square represents 1% of BGCs. (D) The counts of transporter domains per each bacterial BGC that contains at least one transporter gene across MIBiG.