Characterization of the 105-kDa molecular chaperone. Identification, biochemical properties, and localization.
We have characterized the biochemical properties of the testis and brain-specific 105-kDa protein which is cross-reacted with an anti-bovine HSP90 antibody. The protein was induced in germ cells by heat stress, resulting in a protein which is one of the heat shock proteins [Kumagai, J., Fukuda, J., Kodama, H., Murata, M., Kawamura, K., Itoh, H. & Tanaka, T. (2000) Eur. J. Biochem.267, 3073-3078]. In the present study, we characterized the biochemical properties of the protein. The 105-kDa protein inhibited the aggregation of citrate synthase as a molecular chaperone in vitro. ATP/MgCl2 has a slight influence of the suppression of the citrate synthase aggregation by the 105-kDa protein. The protein possessed chaperone activity. The protein was able to bind to ATP-Sepharose like the other molecular chaperone HSP70. A partial amino-acid sequence (24 amino-acid residues) of the protein was determined and coincided with those of the mouse testis- and brain-specific APG-1 and osmotic stress protein 94 (OSP94). The 105-kDa protein was detected only in the medulla of the rat kidney sections similar to OSP94 upon immunoblotting. The purified 105-kDa protein was cross-reacted with an antibody against APG-1. These results suggested that APG-1 and OSP94 are both identical to the 105-kDa protein. There were highly homologous regions between the 105-kDa protein/APG-1/OSP94 and HSP90. The region of HSP90 was also an immunoreactive site. An anti-bovine HSP90 antibody may cross-react with the 105-kDa protein similar to HSP90 in the rat testis and brain. We have investigated the localization and developmental induction of the protein in the rat brain. In the immunohistochemical analysis, the protein was mainly detected in the cytoplasm of the nerve and glial cells of the rat brain. Although the 105-kDa protein was localized in all rat brain segments, the expression pattern was fast in the cerebral cortex and hippocampus and slow in the cerebellum.
Matsumori
Mika
M
Department of Biochemistry, Department of Pediatrics, First Department of Internal Medicine, Third Department of Internal Medicine, Department of Gynecology, and Department of Neurosurgery, Akita University School of Medicine, Akita City, Japan.
Itoh
Hideaki
H
Toyoshima
Itaru
I
Komatsuda
Atsushi
A
Sawada
Ken-Ichi
K
Fukuda
Jun
J
Tanaka
Toshinobu
T
Okubo
Atsuya
A
Kinouchi
Hiroyuki
H
Mizoi
Kazuo
K
Hama
Tokiko
T
Suzuki
Akira
A
Hamada
Fumio
F
Otaka
Michiro
M
Shoji
Yutaka
Y
Takada
Goro
G
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism; D008297:Male; D018832:Molecular Chaperones / Q000737:chemistry*; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000166:cytology; D016716:PC12 Cells; D011485:Protein Binding; D017433:Protein Structure, Secondary; D051381:Rats; D017208:Rats, Wistar; D012685:Sepharose / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000196:embryology / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution
D000255:Adenosine Triphosphate; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D012685:Sepharose; C490980:Hspa4l protein, rat; C099678:Hspa4l protein, mouse