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Table 3 Comparisons of CDF Carriers with Crac Channels1.

From: Animal Ca2+ release-activated Ca2+ (CRAC) channels appear to be homologous to and derived from the ubiquitous cation diffusion facilitators

CDF (2.A.4) Crac-C (1.A.52)
   1. Secondary Carriers: catalyze Me2+:H+ antiport. Channels: catalyze bidirectional Ca2+ flux.
   2. Ubiquitous; in plasma and intracellular membranes of eukaryotes. Present only in eukaryotes; at the plasma membrane/endoplasmic reticulum junctions.
   3. 6 TMSs; N- and C-termini inside; dimeric. 4 TMSs; N- and C-termini inside; tetrameric.
   4. Much size and sequence divergence. Little size and sequence divergence.
   5. Two aspartates are critical for Me2+ binding. Two glutamates are critical for Ca2+ binding.
  1. 1 Abbreviation: Me2+, divalent heavy metal ion;