tailieunhanh - Báo cáo khoa học: Tet repressor mutants with altered effector binding and allostery

To learn about the correlation between allostery and ligand binding of the Tet repressor (TetR) we analyzed the effect of mutations in the DNA read-ing head–core interface on the effector specific TetR i2 variant. The same mutations in these subdomains can lead to completely different activities, . the V99G exchange in the wild-type leads to corepression by 4-ddma-atc without altering DNA binding. However, in TetR i2 it leads to 4-ddma-atc dependent repression in combination with reduced DNA binding in the absence of effector. . | ềFEBS Journal Tet repressor mutants with altered effector binding and allostery Eva-Maria HenBler Ralph Bertram Stefanie Wisshak and Wolfgang Hillen Lehrstuhl fur Mikrobiologie Institut fur Biologie Friedrich-Alexander Universitat Erlangen-Nurnberg Erlangen Germany Keywords allostery effector specificity reverse TetR tetracycline derivatives Tet repressor Correspondence W. Hillen Lehrstuhl fur Mikrobiologie Institut fur Biologie Friedrich-Alexander Universitat Erlangen-Nurnberg StaudtstraBe 5 91058 Erlangen Germany Fax 49 9131 85 28082 Tel 49 9131 85 28081 E-mail whillen@ Received 12 May 2005 revised 12 July 2005 accepted 15 July 2005 doi To learn about the correlation between allostery and ligand binding of the Tet repressor TetR we analyzed the effect of mutations in the DNA reading head-core interface on the effector specific TetRi2 variant. The same mutations in these subdomains can lead to completely different activities . the V99G exchange in the wild-type leads to corepression by 4-ddma-atc without altering DNA binding. However in TetRi2 it leads to 4-ddma-atc dependent repression in combination with reduced DNA binding in the absence of effector. The thermodynamic analysis of effector binding revealed decreased affinities and positive cooperativity. Thus mutations in this interface can influence DNA binding as well as effector binding albeit both ligand binding sites are not in direct contact to these altered residues. This finding represents a novel communication mode of TetR. Thus allostery may not only operate by the structural change proposed on the basis of the crystal structures. Tetracycline tc resistance in Gram-negative bacteria is often regulated by the Tet Repressor TetR a tc-responsive allosterical DNA-binding protein. Due to three very advantageous properties namely the highly specific binding of TetR to tet operator tetO the sensitive induction by small amounts of tc and the ability .

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