Planarian cytochrome b(561): conservation of a six transmembrane structure and localization along the central and peripheral nervous system.
Cytochrome b(561) is a major transmembrane protein of catecholamine and neuropeptide secretory vesicles in the central and peripheral nervous systems of higher animals. We succeeded in cloning a full-length cDNA encoding planarian cytochrome b(561). The deduced amino acid sequence shows a very similar six transmembrane topology to those of cytochromes b(561) of higher vertebrates and contains both putative ascorbate- and monodehydro ascorbate-binding sites. Among the six totally-conserved His residues of cytochrome b(561) in higher vertebrates, one is substituted with an Asn residue, indicating that His88 and His161 of bovine cytochrome b(561) play roles as heme b ligands at the extravesicular side. Northern- and Western-blot analyses confirmed the expression of the mRNA and protein with the expected sizes in planarians. The distributions of the mRNA and apoprotein were analyzed by in situ hybridization and immunohistochemical staining, respectively, showing two morphologically distinct structures, a pair of ventral nerve cords and the cephalic ganglion cluster in the head region. The present results suggest that the usage of ascorbate to supply electron equivalents to neuroendocrine-specific copper-containing monooxygenases is likely to have originated in organisms with a very simple nervous system.
Asada
Akikazu
A
Department of Life Science, Faculty of Science, Himeji Institute of Technology, Kamigoori-cho, Akou-gun, Hyogo 678-1297, Japan.
Kusakawa
Takashi
T
Orii
Hidefumi
H
Agata
Kiyokazu
K
Watanabe
Kenji
K
Tsubaki
Motonari
M
D000595:Amino Acid Sequence; D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002490:Central Nervous System / Q000378:metabolism*; D003001:Cloning, Molecular; D003573:Cytochrome b Group / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015723:Gene Library; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D015394:Molecular Structure; D017933:Peripheral Nervous System / Q000378:metabolism*; D010932:Planarians / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D003573:Cytochrome b Group; D012333:RNA, Messenger; C023646:cytochrome b561; D001205:Ascorbic Acid