Comparative investigations on the amino-acid sequences of different isolectins from the sponge Axinella polypoides (Schmidt).
The sponge Axinella polypoides contains four different D-galactose binding lectins and one, termed lectin IV, which is specific for hexuronic acids. Only the D-galactose binding lectins were investigated in this study. The complete amino-acid sequence of lectin I, the main component in the crude extract was determined. Lectin I is a homodimer and each subunit comprises 144 amino acids with a M(r) of 15,847 +/- 10, as calculated from the sequence data and determined by mass spectrometry. Each subunit contains one intrachain disulfide bridge between positions 4 and 46. Of lectin II, only the first 49 amino acids of the NH2-terminal end were analysed. This part has 29 amino acids in common with lectin I, including a cysteine residue at position 4, also suggesting an intrachain loop in a identical position as in lectin I. The molecular mass of its subunit is 16,235 +/- 10 Da. Only the first 15 NH2-terminal amino acids of lectins III and V could be sequenced. Lectin V was identical to lectin II in all positions, whereas lectin III showed only 5 residues identical to lectins I or II. Thus, lectins I, II and III are derived from three different genes, whereas lectin V may either be a proteolytic cleavage product, or result from different splicing events or may be derived also from a separate gene. Neither of the four lectins showed any similarity to known lectin sequences of animal or plant origin.
Buck
F
F
Institut für Zellbiochemie und klinische Neurobiologie, Universität Hamburg, Germany.
Luth
C
C
Strupat
K
K
Bretting
H
H
D000595:Amino Acid Sequence; D000818:Animals; D037102:Lectins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011161:Porifera / Q000737:chemistry*; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012995:Solubility
D037102:Lectins; D010446:Peptide Fragments; C077149:lectin I, Axinella polypoides