Biomaterial Database

Molecular characterization of limulin, a sialic acid binding lectin from the hemolymph of the horseshoe crab, Limulus polyphemus. 1977

R Kaplan, and S S Li, and J M Kehoe

The sialic acid binding lectin, limulin, was isolated by gel filtration and ion-exchange chromatography from the hemolymph of Limulus polyphemus. When the purified protein was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of beta-mercaptoethanol, two major protein bands were observed. These two bands, subsequently found to contain carbohydrate as well, corresponded to molecular weights of 25 000 and 27 000. Amino acid sequence analyses were performed on both the intact protein and isolated cyanogen bromide fragments. The following primary structural features were noted in the amino-terminal region of limulin: (1) the absence of histidine and alanine from the NH2-terminal 50 residues; (2) the presence of five of the total eight prolines of the molecule between positions 13 and 30; and (3) a possible carbohydrate attachment site consisting of only the amino acids proline and serine between residues 13 and 19. The resultsof cyanogen bromide cleavage studies confirmed the presence of 2 methionine residues per subunit, at positions 25 and 58 respectively. No sequence heterogeneity was observed in this study. While it is quite possible that limulin plays some role in the defense mechanisms of the horseshoe crab, there is no obvious sequence homology between this invertebrate lectin and vertebrate immunoglobulins.

UI	MeSH Term	Description	Entries
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D005779	Immunodiffusion	Technique involving the diffusion of antigen or antibody through a semisolid medium, usually agar or agarose gel, with the result being a precipitin reaction.	Gel Diffusion Tests,Diffusion Test, Gel,Diffusion Tests, Gel,Gel Diffusion Test,Immunodiffusions,Test, Gel Diffusion,Tests, Gel Diffusion
D006386	Hemagglutination Tests	Sensitive tests to measure certain antigens, antibodies, or viruses, using their ability to agglutinate certain erythrocytes. (From Stedman, 26th ed)	Hemagglutination Test,Test, Hemagglutination,Tests, Hemagglutination
D006388	Hemagglutinins	Agents that cause agglutination of red blood cells. They include antibodies, blood group antigens, lectins, autoimmune factors, bacterial, viral, or parasitic blood agglutinins, etc.	Isohemagglutinins,Exohemagglutinins,Hemagglutinin
D006458	Hemolymph	The blood/lymphlike nutrient fluid of some invertebrates.	Hemolymphs
D006737	Horseshoe Crabs	An arthropod subclass (Xiphosura) comprising the North American (Limulus) and Asiatic (Tachypleus) genera of horseshoe crabs.	Crabs, Horseshoe,Limulus,Limulus polyphemus,Tachypleus,Xiphosura,Crab, Horseshoe,Horseshoe Crab,Xiphosuras
D000373	Agglutinins	A substance that makes particles (such as bacteria or cells) stick together to form a clump or a mass.	Agglutinin
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino