Abstract
Binding of thiamine to thiamine-binding protein is reversible, with a dissociation constant for the thiamine-binding protein-thiamine complex of about 9nM. The optimal pH for the binding is between pH 8 to 9. Thiamine analogues such as thiamine monophosphate and chloroethylthiamine competitively inhibit the binding with a Ki value of 3.4×10^<-9>M and 6.8×10^<-7>M respectively. Among various modifying reagents for protein testeld, dimethyl (2-hydroxy-5-nitrobenzyl)-sulfonium bromide which is considered to modify tryptophan residue of the protein, effectively inhibited both the binding of thiamine to thiamine-binding protein and thiamine uptake by whole cells suggesting that tryptophan is involved in the thiamine binding site of thiamine-binding protein in thiamine transport system of E.coli,
