Table 8. The performance (coverage metric) of the PSI-BLAST search on the main dataset using a five-fold cross-validation.

Transporter class	Coverage (%) at E-value cutoff thresholds
	1E-4	1E-10	1E-50
Amino acid	74.29	74.29	52.86
Anion	40.00	38.33	31.67
Cation	68.46	62.69	41.54
Electron	30.00	30.00	13.33
Protein/mRNA	34.29	32.86	21.43
Sugar	68.33	65.00	51.67
Other	59.00	56.50	38.50
Non-transporter	34.67	25.50	7.67