A sialic acid-binding lectin (Hericium erinaceum lectin, HEL), isolated from fresh fruiting bodies of Hericium erinaceum, was treated with various temperature and pH to investigate its fluorescence spectra and hemagglutinating activity. It was found that the hemagglutinating activity of HEL was relatively steady below 60 °C and at pH from 6 to 11, and the change of hemagglutinating activity was relative to the change of hydrophobic areas where tryptophan residues located. In fluorescence quenching study of HEL by acrylamide and KI, it was indicated that nearly all the tryptophan residues of HEL located on the surface of the molecule, and most of them were in hydrophobic areas or negatively charged areas. Chemical modification of HEL proved that there were about twelve tryptophan residues in a HEL molecule and all of them were located on the surface or in the shallow groove of the molecule, and eight of them were essential for hemagglutinating activity; aspartic acid or glutamic acid residues were involved in maintaining the crucial conformation of activity center and made great contribution to the hemagglutinating activity of HEL, but they could not touch the sialic acid molecule directly; tyrosine residues also played a role in the hemagglutinating activity of HEL; while arginine, serine, threonine, histidine residues had no effect on the hemagglutinating activity of HEL.
Key wordssialic acid-binding lectin; Hericium erinaceum lectin; fluorescence spectrum and fluorescence quenching; hemagglutinating activity; chemical modification In a broad sense, lectins are proteins or glycoproteins of non-immune origin that bind specifically to carbohydrates [1]. But most lectins are usually multivalent, which means they have more than one carbohydrate-binding site in one molecule, a property that enables them to agglutinate erythrocytes and other cells [2,3]. Some lectins exhibit bloodgroup specificity [4] and can be used in blood grouping; some agglutinate transformed cells better than the normal ones [5]. Therefore, clinical researcher can benefit from this property in developing new diagnostic approaches and treatments of cancer. Lectins distribute ubiquitously in animals, plants, microorganism, and even virus. They have Received: February, 16, 2004 Accepted: April, 20, 2004 This work was supported by a grant from the National Natural Science Foundation of China (General Program) (No. 30000032) *Corresponding author: Tel, 86-28-8541-0672; E-mail, jinkubao@yahoo. com various functions, which are, however, not clear even now [2]. The lectins distributed in fungi much wider than in higher plants, and they play many important roles in symbiotic or parasitic behavior, growth and morphogenesis of fungi [6]. Hericium erinaceum, also called monkey-head mushroom or lion's mane, is well known as a rare traditional Chinese medicine and delicious edible mushroom. A sialic acid-binding lectin (Hericium erinaceum lectin, HEL) was isolated from Hericium erinaceum. The molecular mass of intact HEL is estimated to be 54 kD....