5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamide(in) + (6S)-5-methyl-5,6,7,8-tetrahydrofolate(out) = 5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamide(out) + (6S)-5-methyl-5,6,7,8-tetrahydrofolate(in) — reaction