Six‐fold rotational symmetry of ClpQ, the E. coli homolog of the 20S proteasome, and its ATP‐dependent activator, ClpY

FEBS Letters

Wu, Whi-fin¹  Kocsis, Eva³  Gottesman, Susan¹  Maurizi, Michael R.²  Kessel, Martin³  Steven, Alasdair C.³ 

[1] Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bldg. 37, Rm. 1 B07, 37 Convent Drive, MSC 4255, Bethesda, MD 20892-2755, USA;Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA;Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA

关键词: Clp protease;    Hs1U/HsIV;    ATP-dependent protease;    Proteasome;    Rotational symmetry;    Image analysis;   

DOI  :  10.1016/S0014-5793(96)01261-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

ClpQ (HsIV) is a homolog of the β-subunits of the 20S proteasome. In E. coli, it is expressed from an operon that also encodes ClpY (HsIU), an ATPase homologous to the protease chaperone, ClpX. ClpQ (subunit M _r 19 000) and ClpY (subunit M _r 49 000) were purified separately as oligomeric proteins with molecular weights of ∼220 000 and ∼350 000, respectively, estimated by gel filtration. Mixtures of ClpY and ClpQ displayed ATP-dependent proteolytic activity against casein, and a complex of the two proteins was isolated by gel filtration in the presence of ATP. Image processing of negatively stained electron micrographs revealed strong six-fold rotational symmetry for both ClpY and ClpQ, suggesting that the subunits of both proteins are arranged in hexagonal rings. The molecular weight of ClpQ combined with its symmetry is consistent with a double hexameric ring, whereas the data on ClpY suggest only one such ring. The symmetry mismatch previously observed between hexameric ClpA and heptameric ClpP in the related ClpAP protease is apparently not reproduced in the symmetry-matched ClpYQ system.

【 授权许可】

Unknown