Striking sequence similarity among sialic acid-binding lectin, pancreatic ribonucleases, and angiogenin: possible structural and functional relationships.

We found that a sialic acid-binding lectin (SABL) from bullfrog egg bears a remarkable degree of similarity with human angiogenin and the pancreatic ribonucleases (EC 3.1.27.5). Based on (1) the conservation of several disulfide bond-forming cysteines, (2) a cluster of nonpolar residues, and (3) a number of active-site residues of bovine ribonuclease, we propose that SABL has essentially the same secondary and tertiary structures and very likely has ribonuclease activity. Other possible physiological roles are discussed.