Table 17.

Distribution of transporter families in the three domains of lifea

Transporter typeNo. of families per group
BAEBABEAEBAE
Channels
 Protein channels20170003
 Protein toxins8010100
 Peptide toxins11040000
 Holins16000000
 Porins22010000
 Total590230103
Secondary carriers2301235027
Primary carriers(6–10)421(1–5)16
Group translocators6000000
Unknown8063102
 Total102443712138
  • 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.