Novel rhamnose-binding lectins from the colonial ascidian Botryllus schlosseri.
In a full-length cDNA library from the compound ascidian Botryllus schlosseri, we identified, by BLAST search against UniProt database, five transcripts, each with complete coding sequence, homologous to known rhamnose-binding lectins (RBLs). Comparisons of the predicted amino acid sequences suggest that they represent different isoforms of a novel RBL, called BsRBL-1-5. Four of these isolectins were found in Botryllus homogenate after purification by affinity chromatography on acid-treated Sepharose, analysis by reverse-phase HPLC and mass spectrometry. Analysis of both molecular masses and tryptic digests of BsRBLs indicated that the N-terminal sequence of the purified proteins starts from residue 22 of the putative amino acid sequence, and residues 1-21 represent a signal peptide. Analysis by mass spectrometry of V8-protease digests confirmed the presence and alignments of the eight cysteines involved in the disulphide bridges that characterise RBLs. Functional studies proved the enhancing effect on phagocytosis of the affinity-purified material. Results are discussed in terms of phylogenetic relationships of BsRBLs with orthologous molecules from protostomes and deuterostomes.
Gasparini
Fabio
F
Dipartimento di Biologia and CRIBI, University of Padova, Padova, Italy.
Franchi
Nicola
N
Spolaore
Barbara
B
Ballarin
Loriano
L
D000373:Agglutinins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D017124:Conserved Sequence; D004220:Disulfides / Q000378:metabolism; D005697:Galactosides / Q000378:metabolism; D037102:Lectins / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010455:Peptides / Q000032:analysis / Q000737:chemistry; D010587:Phagocytosis / Q000187:drug effects; D010802:Phylogeny; D012210:Rhamnose / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry; D014158:Transcription, Genetic / Q000235:genetics; D014561:Urochordata / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D000373:Agglutinins; D004220:Disulfides; D005697:Galactosides; D037102:Lectins; D010455:Peptides; D012210:Rhamnose; D002118:Calcium