SPECIFICITY OF THE SIALIC ACID-BINDING LECTIN FROM OVINE PLACENTA

TRONCOSO, MARÍA FERNANDA; IGLESIAS, MARÍA MERCEDES; ISECKE, RAINER; WOLFENSTEIN-TODEL, CARLOTA; BROSSMER REINHARD

Fortaleza, Ceará, Brasil

Congreso; 19th International Lectin Meeting, (INTERLEC 19); 2001

Sialic acids (Sias) are a family of acidic nine-carbon sugars distributed on cell surfaces as terminal components of glycoconjugates and also occurring as part of many glycoproteins of the body fluid. Sias are known to play important roles in a variety of biological processes, such as: infection of cells by microorganisms, regulation of the immune system, development of the nervous system and cancer metastasis. A sialic acid-binding lectin was isolated from ovine placenta (OPL I) by Iglesias et al. [1]. The aim of this work was to establish the molecular features of the protein-carbohydrate interaction of this lectin. The specificity of the lectin was examined in detail by haemagglutination inhibition assays applying a panel of 32 synthetic sialic acid analogues. These experiments lead to the conclusion that the carboxylic acid group is a prerequisite for the interaction with the lectin, the alpha-anomer of the methyl glycoside is only a little more effective as an inhibitor than the beta-anomer and the most potent inhibitor was 9-deoxy-10-carboxylic acid Neu5Ac, followed by 4-oxo-Neu5Ac. In contrast to the majority of known sialic acid-binding lectins, the N-acetyl group of Neu5Ac is not indispensable for binding, neither is the hydroxyl group at C-9 since substitutions at this carbon atom are well tolerated. Furthermore, all sulfur-containing substituents at C-9 enhanced the affinity of the lectin. This is the first sialic acid-binding lectin found to strongly bind thio derivatives.[1] Iglesias MM, Cymes GD, Wolfenstein-Todel C (1996) Glycoconj J 13: 967-76.