title: Molecular Basis and Consequences of the Cytochrome c-tRNA Interaction.
abstract: The intrinsic apoptosis pathway occurs through the release of mitochondrial cytochrome c to the cytosol, where it promotes activation of the caspase family of proteases. The observation that tRNA binds to cytochrome c revealed a previously unexpected mode of apoptotic regulation. However, the molecular characteristics of this interaction, and its impact on each interaction partner, are not well understood. Using a novel fluorescence assay, we show here that cytochrome c binds to tRNA with an affinity comparable with other tRNA-protein binding interactions and with a molecular ratio of ∼3:1. Cytochrome c recognizes the tertiary structural features of tRNA, particularly in the core region. This binding is independent of the charging state of tRNA but is regulated by the redox state of cytochrome c. Compared with reduced cytochrome c, oxidized cytochrome c binds to tRNA with a weaker affinity, which correlates with its stronger pro-apoptotic activity. tRNA binding both facilitates cytochrome c reduction and inhibits the peroxidase activity of cytochrome c, which is involved in its release from mitochondria. Together, these findings provide new insights into the cytochrome c-tRNA interaction and apoptotic regulation.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Cuiping
authors.initials: C
authors.lastname: Liu
authors.affiliation: the Department of Cancer Biology and Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Stonestrom
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Thomas
authors.initials: T
authors.lastname: Christian
authors.affiliation: the Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455.
authors.forename: Jeongsik
authors.initials: J
authors.lastname: Yong
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Takase
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, ya-ming.hou@jefferson.edu.
authors.forename: Ya-Ming
authors.initials: YM
authors.lastname: Hou
authors.affiliation: the Department of Cancer Biology and Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and xyang@mail.med.upenn.edu.
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Yang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D012343:RNA, Transfer / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D045304:Cytochromes c; D012343:RNA, Transfer
keywords: apoptosis; caspase; cytochrome c; mitochondrial apoptosis; transfer RNA (tRNA)