A rainbow trout lectin with multimeric structure

A novel lectin has been identified in rainbow trout serum and plasma. The lectin binds to Sepharose (an agarose polymer) in a calcium-dependent manner. Glucose, N-acetyl-glucosamine, mannose, N-acetyl-mannosamine, L-fucose, maltose and alpha-methyl-mannoside are good inhibitors of this binding, whereas glucosamine and D-fucose inhibits to a lesser degree and mannosamine and galactose do not inhibit, the binding to Sepharose. When analysed by SDS-PAGE under non-reducing conditions, the lectin appears as a characteristic ladder of bands with approximately 16 kDa between consecutive bands. Upon reduction, the lectin appears as a 16-kDa band. On size-exclusion chromatography of trout serum and plasma, the protein emerges over a broad range corresponding to sizes from about 2000 kDa to less than 200 kDa. The NH2-terminal sequence (AAENRNQXPPG) shows no significant homology with known proteins. Because of the characteristic appearance in non-reducing SDS-PAGE and the lectin activity, we propose to name the protein ''ladderlectin.'' (C) 1997 Elsevier Science Inc.