High-affinity transporter for the intake of thiamine. H(+)(in) + thiamine(out) = H(+)(out) + thiamine(in) Optimum pH is 8-8.5. Ubiquitous; most abundant in skeletal and cardiac muscle. Medium expression in placenta, heart, liver and kidney, low in lung. The disease is caused by variants affecting the gene represented in this entry. Belongs to the reduced folate carrier (RFC) transporter (TC 2.A.48) family. Truncated N-terminus.