The highly abundant protein Ag-lbp55 from Ascaridia galli represents a novel type of lipid-binding proteins.
Lipid-binding proteins exhibit important functions in lipid transport, cellular signaling, gene transcription, and cytoprotection. Their functional analogues in nematodes are nematode polyprotein allergens/antigens and fatty acid and retinoid-binding proteins. This work describes a novel 55-kDa protein, Ag-lbp55, purified from the parasitic nematode Ascaridia galli. By direct N-terminal sequencing, a partial amino acid sequence was obtained that allowed the design of oligonucleotide primers to obtain the full-length cDNA sequence. Sequence analysis revealed the presence of an N-terminal signal peptide of 25 amino acid residues and a FAR domain at the C terminus. Data base searches showed almost no significant homologies to other described proteins. The secondary structure of Ag-lbp55 was predominantly alpha-helical (65%) as shown by CD spectroscopy. It was found to bind with high affinity fatty acids (caprylic, oleic, and palmitic acid) and their fluorescent analogue dansylaminoundecanic acid. Immunolocalization showed that Ag-lbp55 is a highly abundant protein, mainly distributed in the inner hypodermis and extracellularly in the pseudocoelomatic fluid. A similar staining pattern was observed in other pathogenic nematodes, indicating the existence of similar proteins in these species.
Jordanova
Rositsa
R
Institute of Experimental Pathology and Parasitology, Sofia 1113, Bulgaria.
Radoslavov
Georgi
G
Fischer
Peter
P
Torda
Andrew
A
Lottspeich
Friedrich
F
Boteva
Raina
R
Walter
Rolf D
RD
Bankov
Ilia
I
Liebau
Eva
E
D000595:Amino Acid Sequence; D000818:Animals; D001197:Ascaridia / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D002210:Caprylates / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry; D002942:Circular Dichroism; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D050556:Fatty Acid-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D007150:Immunohistochemistry; D008024:Ligands; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry*; D008954:Models, Biological; D008969:Molecular Sequence Data; D019301:Oleic Acid / Q000737:chemistry; D009841:Oligonucleotides / Q000737:chemistry; D019308:Palmitic Acid / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014158:Transcription, Genetic
D002210:Caprylates; D002352:Carrier Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D050556:Fatty Acid-Binding Proteins; D008024:Ligands; D008055:Lipids; D009841:Oligonucleotides; D010455:Peptides; D019301:Oleic Acid; D019308:Palmitic Acid; C031492:octanoic acid