The carboxy‐terminal domain of the LexA repressor oligomerises essentially as the entire protein

FEBS Letters

Hurstel, Serge¹  Schnarr, Manfred¹  Pouyet, Jean¹  Granger-Schnarr, Michèle¹ 

[1] Institut de Biologie Moléculaire et Cellulaire, CNRS and Université Louis Pasteur, 15, rue René Descartes, 67084 Strasbourg Cedex, France

关键词: SOS system;    LexA repressor;    RecA protein;    DNA-binding protein;    Multi-domain protein;    Equilibrium ultracentrifugation;   

DOI  :  10.1016/0014-5793(88)81302-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The ability of the isolated carboxy-terminal domain of the LexA repressor of Escherichia coli to form dimers and tetramers has been investigated by equilibrium ultracentrifugation. This domain, that comprises the amino acids 85–202, is readily purified after self-cleavage of the LexA repressor at alkaline pH. It turns out that the carboxy-terminal domain forms dimers and tetramers essentially as the entire LexA repressor. The corresponding association constants were determined after non-linear least squares fitting of the experimental concentration distribution. A dimer association constant of K ₂ = 3 × 10⁴ M⁻¹ and a tetramer association constant of K ₄ = 2 × 10⁴ M⁻¹ have been determined. Similar measurements on the entire LexA repressor [(1985) Biochemistry 24, 2812–2818] gave values of K ₂ = 2.1 × 10⁴ M⁻¹ and K ₄ = 7.7 × 10⁴ M⁻¹. Within experimental error the dimer formation constant of the carboxy-terminal domain may be considered to be the same as that of the entire repressor whereas the isolated domain forms tetramers slightly less efficiently. It should be stressed that the potential error in K ₄ is higher than that in K ₂. The overall conclusion is that the two structural domains of LexA have also well-defined functional roles: the amino-terminal domain interacts with DNA and the carboxy-terminal domain is involved in dimerisation reinforcing in this way the binding of the LexA repressor to operator DNA.

【 授权许可】

Unknown