Stable association of 70-kDa heat shock protein induces latent multisite specificity of a unisite-specific endonuclease in yeast mitochondria.
The multisite-specific endonuclease Endo.SceI of yeast mitochondria is unique among endonucleases because its 50-kDa subunit forms a stable dimer with the mitochondrial 70-kDa heat shock protein (mtHSP70), which otherwise fulfills a chaperone function by binding transiently to unfolded proteins. Here we show that the mtHSP70 subunit confers broader sequence specificity, greater stability, and higher activity on the 50-kDa subunit. The 50-kDa subunit alone displayed weaker activity and highly sequence-specific endonuclease activity. The 50-kDa protein exists as a heterodimer with mtHSP70 in vivo, allowing Endo.SceI to cleave specifically at multiple sites on mitochondrial DNA. Endo.SceI may have evolved from a highly specific endonuclease that gained broader sequence specificity after becoming a stable partner of mtHSP70.
Mizumura
H
H
Laboratory of Cellular and Molecular Biology, RIKEN (the Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan.
Shibata
T
T
Morishima
N
N
D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D004790:Enzyme Induction; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity
D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific