VanabinP, a novel vanadium-binding protein in the blood plasma of an ascidian, Ascidia sydneiensis samea.
Some ascidians accumulate high levels of the transition metal vanadium in their blood cells. The process of vanadium accumulation has not yet been elucidated. In this report, we describe the isolation and cDNA cloning of a novel vanadium-binding protein, designated as VanabinP, from the blood plasma of the vanadium-rich ascidian, Ascidia sydneiensis samea. The predicted amino acid sequence of VanabinP was highly conserved and similar to those of other Vanabins. The N-terminus of the mature form of VanabinP was rich in basic amino acid residues. VanabinP cDNA was originally isolated from blood cells, as were the other four Vanabins. However, Western blot analysis revealed that the VanabinP protein was localized to the blood plasma and was not detectable in blood cells. RT-PCR analysis and in situ hybridization indicated that the VanabinP gene was transcribed in some cell types localized to peripheral connective tissues of the alimentary canal, muscle, blood cells, and a portion of the branchial sac. Recombinant VanabinP bound a maximum of 13 vanadium(IV) ions per molecule with a Kd of 2.8 x 10(-5) M. These results suggest that VanabinP is produced in several types of cell, including blood cells, and is immediately secreted into the blood plasma where it functions as a vanadium(IV) carrier.
Yoshihara
Masao
M
Molecular Physiology Laboratory, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan.
Ueki
Tatsuya
T
Watanabe
Takahiro
T
Yamaguchi
Nobuo
N
Kamino
Kei
K
Michibata
Hitoshi
H
D000595:Amino Acid Sequence; D024361:Amino Acids, Basic / Q000737:chemistry; D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D010949:Plasma / Q000737:chemistry*; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014561:Urochordata / Q000737:chemistry / Q000378:metabolism*; D014639:Vanadium / Q000378:metabolism*
D024361:Amino Acids, Basic; D002352:Carrier Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014639:Vanadium