TABLE 17.
Distribution of transporter families in the three domains of lifea
| Transporter type | No. of families per group
|
||||||
|---|---|---|---|---|---|---|---|
| B | A | E | BA | BE | AE | BAE | |
| Channels | |||||||
| Protein channels | 2 | 0 | 17 | 0 | 0 | 0 | 3 |
| Protein toxins | 8 | 0 | 1 | 0 | 1 | 0 | 0 |
| Peptide toxins | 11 | 0 | 4 | 0 | 0 | 0 | 0 |
| Holins | 16 | 0 | 0 | 0 | 0 | 0 | 0 |
| Porins | 22 | 0 | 1 | 0 | 0 | 0 | 0 |
| Total | 59 | 0 | 23 | 0 | 1 | 0 | 3 |
| Secondary carriers | 23 | 0 | 12 | 3 | 5 | 0 | 27 |
| Primary carriers | (6–10) | 4 | 2 | 1 | (1–5) | 1 | 6 |
| Group translocators | 6 | 0 | 0 | 0 | 0 | 0 | 0 |
| Unknown | 8 | 0 | 6 | 3 | 1 | 0 | 2 |
| Total | 102 | 4 | 43 | 7 | 12 | 1 | 38 |
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.