A Drosophila haemocyte-specific protein, hemolectin, similar to human von Willebrand factor.
We identified a novel Drosophila protein of approximately 400 kDa, hemolectin (d-Hml), secreted from haemocyte-derived Kc167 cells. Its 11.7 kbp cDNA contains an open reading frame of 3843 amino acid residues, with conserved domains in von Willebrand factor (VWF), coagulation factor V/VIII and complement factors. The d-hml gene is located on the third chromosome (position 70C1-5) and consists of 26 exons. The major part of d-Hml consists of well-known motifs with the organization: CP1-EG1-CP2-EG2-CP3-VD1-VD2-VD'-VD3-VC1-VD"-VD"'-FC1-FC2-VC2-LA1-VD4-VD5-VC3-VB1-VB2-VC4-VC5-CK1 (CP, complement-control protein domain; EG, epidermal-growth-factor-like domain; VB, VC, VD, VWF type B-, C- and D-like domains; VD', VD", VD"', truncated C-terminal VDs; FC, coagulation factor V/VIII type C domain; LA, low-density-lipoprotein-receptor class A domain; CK, cysteine knot domain). The organization of VD1-VD2-VD'-VD3, essential for VWF to be processed by furin, to bind to coagulation factor VIII and to form interchain disulphide linkages, is conserved. The 400 kDa form of d-Hml was sensitive to acidic cleavage near the boundary between VD2 and VD', where the cleavage site of pro-VWF is located. Agarose-gel electrophoresis of metabolically radiolabelled d-Hml suggested that it is secreted from Kc167 cells mainly as dimers. Resembling VWF, 7.9% (305 residues) of cysteine residues on the d-Hml sequence had well-conserved positions in each motif. Coinciding with the development of phagocytic haemocytes, d-hml transcript was detected in late embryos and larvae. Its low-level expression in adult flies was induced by injury at any position on the body.
Goto
A
A
Graduate Program for Regulation of Biological Signals, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi 464-8601, Japan.
Kumagai
T
T
Kumagai
C
C
Hirose
J
J
Narita
H
H
Mori
H
H
Kadowaki
T
T
Beck
K
K
Kitagawa
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D002875:Chromosomes / Q000235:genetics; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D018507:Gene Expression Regulation, Developmental; D006434:Hemocytes / Q000378:metabolism*; D006801:Humans; D037102:Lectins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014841:von Willebrand Factor / Q000737:chemistry
D017931:DNA Primers; D018076:DNA, Complementary; D004220:Disulfides; D029721:Drosophila Proteins; C476120:Hml protein, Drosophila; D037102:Lectins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D014841:von Willebrand Factor