title: Primary structures of two hemagglutinins from the marine red alga, Hypnea japonica.
abstract: As the first examples among marine algal hemagglutinins, the primary structures of two hemagglutinins, named hypnin A-1 and A-2, from the red alga Hypnea japonica, were determined by Edman degradation. Both hemagglutinins were single-chain polypeptides composed of 90 amino acid residues including four half-cystines, all of which were involved in two intrachain disulfide bonds, Cys(5)-Cys(62) and Cys(12)-Cys(89). Hypnin A-1 and A-2 had calculated molecular masses of 9146.7 and 9109.7 Da which coincided with determined values, 9148 and 9109 Da, by electrospray ionization-mass spectrometry, respectively. Both hemagglutinins only differed from each other at three positions; Pro(19), Arg(31) and Phe(52) of hypnin A-1 as compared with Leu(19), Ser(31), and Tyr(52) of hypnin A-2. Approximately 43% of total residual numbers consisted of three kinds of amino acids: serine, glycine and proline. The hemagglutination activities were lost by reduction and alkylation of the disulfide bonds. The nature of the small-sized polypeptides, including disulfide bonds, may contribute to the extreme thermostability of the hemagglutinins. Sequence having overall similarity to hypnin A-1 or A-2 was not detected in databases. Unexpectedly, however, hypnins contained a motif similar to the alignment of the C-terminal conserved amino acids within carbohydrate-recognition domains of C-type animal lectins. Furthermore, interestingly, the hemagglutination activities were inhibited by a protein, phospholipase A-2 besides some glycoproteins, suggesting that hypnins may possess both a protein-recognition site(s) and a carbohydrate-recognition site(s).
authors.affiliation: Faculty of Applied Biological Science, Hiroshima University, Kagamiyama 1-4-4, Higashi-Hiroshima, Japan. kanhori@ipc.hiroshima-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Hori
authors.forename: K
authors.initials: K
authors.lastname: Matsubara
authors.forename: K
authors.initials: K
authors.lastname: Miyazawa
mesh_terms: D000595:Amino Acid Sequence; D004220:Disulfides / Q000737:chemistry; D006388:Hemagglutinins / Q000737:chemistry*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010741:Phospholipases A / Q000494:pharmacology; D000461:Rhodophyta / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
chemical_list: D004220:Disulfides; D006388:Hemagglutinins; D010741:Phospholipases A