Table 17.

Distribution of transporter families in the three domains of lifea

Transporter typeNo. of families per group
 Protein channels20170003
 Protein toxins8010100
 Peptide toxins11040000
Secondary carriers2301235027
Primary carriers(6–10)421(1–5)16
Group translocators6000000
  • a Numbers that are boldface and underlined represent the major organismal grouping(s) (B, bacteria; A, archaea; E, eukaryotes; BE, bacteria and eukaryotes; BAE, bacteria, archaea, and eukaryotes) in which each transporter type is found. For the primary carriers, the bold number in parentheses refers to the organismal distribution; the nonbold numbers are the values that would result if mitochondria and chloroplasts are considered to be of bacterial origin. Data are as of 1 January 1999.