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413 results on '"Oka, Toshihiko"'

2. Localization of myoglobin in mitochondria: implication in regulation of mitochondrial respiration in rat skeletal muscle.

Author

Koma, Rikuhide, Shibaguchi, Tsubasa, Pérez López, Claudia, Oka, Toshihiko, Jue, Thomas, Takakura, Hisashi, and Masuda, Kazumi

Subjects
myoglobin, proteinase K, skeletal muscle, submitochondrial localization, Physiology, Clinical Sciences, Medical Physiology
Abstract

Mitochondria play a principal role in metabolism, and mitochondrial respiration is an important process for producing adenosine triphosphate. Recently, we showed the possibility that the muscle-specific protein myoglobin (Mb) interacts with mitochondrial complex IV to augment the respiration capacity in skeletal muscles. However, the precise mechanism for the Mb-mediated upregulation remains under debate. The aim of this study was to ascertain whether Mb is truly integrated into the mitochondria of skeletal muscle and to investigate the submitochondrial localization. Isolated mitochondria from rat gastrocnemius muscle were subjected to different proteinase K (PK) concentrations to digest proteins interacting with the outer membrane. Western blotting analysis revealed that the PK digested translocase of outer mitochondrial membrane 20 (Tom20), and the immunoreactivity of Tom20 decreased with the amount of PK used. However, the immunoreactivity of Mb with PK treatment was better preserved, indicating that Mb is integrated into the mitochondria of skeletal muscle. The mitochondrial protease protection assay experiments suggested that Mb localizes within the mitochondria in the inner membrane from the intermembrane space side. These results strongly suggest that Mb inside muscle mitochondria could be implicated in the regulation of mitochondrial respiration via complex IV.

Published
2021

5. A novel approach for structure analysis of two-dimensional membrane protein crystals using x-ray powder diffraction data

Author

Dilanian, Ruben A., Darmanin, Connie, Varghese, Jose N., Wilkins, Steve W., Oka, Toshihiko, Yagi, Naoto, Quiney, Harry M., and Nugent, Keith A.

Subjects
Physics - Optics, Physics - Biological Physics
Abstract

The application of powder diffraction methods in two-dimensional crystallography is regarded as intractable because of the uncertainties associated with overlapping reflections. Here, we report an approach that resolves these ambiguities and provides reliable low-resolution phase information directly from powder diffraction data. We apply our method to the recovery of the structure of the bacteriorhodopsin (bR) molecule to a resolution of 7 angstroms using only powder diffraction data obtained from two-dimensional purple membrane (PM) crystals., Comment: 14 pages, 4 figures, 3 tables

Published
2010

14. Physicochemical Properties of the Mammalian Molecular Chaperone HSP60

Author

Ishida, Ryuichi, Okamoto, Tomoya, Motojima, Fumihiro, Kubota, Hiroshi, Takahashi, Hiroki, Tanabe, Masako, Oka, Toshihiko, Kitamura, Akira, Kinjo, Masataka, Yoshida, Masasuke, Otaka, Michiro, Grave, Ewa, Itoh, Hideaki, Ishida, Ryuichi, Okamoto, Tomoya, Motojima, Fumihiro, Kubota, Hiroshi, Takahashi, Hiroki, Tanabe, Masako, Oka, Toshihiko, Kitamura, Akira, Kinjo, Masataka, Yoshida, Masasuke, Otaka, Michiro, Grave, Ewa, and Itoh, Hideaki

Abstract

The E. coli GroEL/GroES chaperonin complex acts as a folding cage by producing a bullet-like asymmetric complex, and GroEL exists as double rings regardless of the presence of adenosine triphosphate (ATP). Its mammalian chaperonin homolog, heat shock protein, HSP60, and co-chaperonin, HSP10, play an essential role in protein folding by capturing unfolded proteins in the HSP60/HSP10 complex. However, the structural transition in ATPase-dependent reaction cycle has remained unclear. We found nucleotide-dependent association and dissociation of the HSP60/HSP10 complex using various analytical techniques under near physiological conditions. Our results showed that HSP60 exist as a significant number of double-ring complexes (football- and bullet-type complexes) and a small number of single-ring complexes in the presence of ATP and HSP10. HSP10 binds to HSP60 in the presence of ATP, which increased the HSP60 double-ring formation. After ATP is hydrolyzed to Adenosine diphosphate (ADP), HSP60 released the HSP10 and the dissociation of the double-ring to single-rings occurred. These results indicated that HSP60/HSP10 undergoes an ATP-dependent transition between the single- and double-rings in their system that is highly distinctive from the GroEL/GroES system particularly in the manner of complex formation and the roles of ATP binding and hydrolysis in the reaction cycle.

Published
2023

16. Insights into the regulation of mitochondrial functions by protein kinase A-mediated phosphorylation.

Author

Akabane, Shiori and Oka, Toshihiko

Subjects
*MITOCHONDRIAL proteins, *PROTEIN kinases, *NUCLEAR proteins, *CYCLIC adenylic acid, *PHOSPHORYLATION
Abstract

Cyclic AMP (cAMP)—protein kinase A (PKA) signaling is a highly conserved pathway in eukaryotes and plays a central role in cell signaling cascades in response to environmental changes. Elevated cAMP levels promote the activation of PKA, which phosphorylates various downstream proteins. Many cytosolic and nuclear proteins, such as metabolic enzymes and transcriptional factors, have been identified as substrates for PKA, suggesting that PKA-mediated regulation occurs predominantly in the cytosol. Mitochondrial proteins are also phosphorylated by PKA, and PKA-mediated phosphorylation of mitochondrial proteins is considered to control a variety of mitochondrial functions, including oxidative phosphorylation, protein import, morphology and quality control. In this review, we outline PKA mitochondrial substrates and summarize the regulation of mitochondrial functions through PKA-mediated phosphorylation. [ABSTRACT FROM AUTHOR]

Published
2024
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41. Light-induced unfolding of photoactive yellow protein mutant M100L

Author

Sasaki, Jun, Kumauchi, Masato, Hamada, Norio, Oka, Toshihiko, and Tokunaga, Fumio

Subjects
Biochemistry -- Research, Proteins -- Genetic aspects, Phototropism -- Physiological aspects, Bacteria -- Physiological aspects, Circular dichroism -- Analysis, Biological sciences, Chemistry
Abstract

Research has been conducted on the photoactive yellow protein which triggers the phototactic response in a phototropic bacterium. The transient conformational changes of the protein's photocycle have been investigated via the circular dichroism spectroscopy and the small-angle X-ray scattering measurements.

Published
2002

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