PURIFICATION AND PROPERTIES OF THIAMINE-BINDING PROTEINS FROM SESAME SEED

Three thiamine-binding proteins of 17-19 kDa (STBP-I, II, and III) wer e purified from sesame seed (Sesamum indicum L.). Each of the proteins was composed of two subunits of equal molecular mass and each subunit consisted of a large polypeptide and a small polypeptide linked by a disulfide bond(s). They were rich in glutamic acid (or glutamine) and arginine. Their binding activities were optimal at neutral pH. They bo und specifically free thiamine but not thiamine phosphates. STBP-I had higher affinity for thiamine than STBP-II or STBP-III. STBP-II and ST BP-III bound one molecule of thiamine per molecule, and STBP-I bound 0 .5 molecule. The amino acid composition and structure of the STPBs wer e similar to those of 2S storage proteins.