The binding of C10 oligomers to XXXX transcription termination factor Rho.

@entity47295 @entity535 @entity50449 @entity24427 @entity280 @entity70984 @entity65127 @entity70983 @entity70985 @entity526
The binding of C10 RNA oligomers to wild type and mutant @entity526 transcription termination factor Rho provides a model for the enzyme-RNA interactions that lead to transcription termination. One surprising finding is that wild type Rho binds between five and six C10 oligomers per hexamer with KD = 0.3 microm, and five to six additional C10 molecules with KD = 7 microm. Previously, approximately half this number of oligomer-binding sites was reported (Wang, Y., and @entity280 . H. (1993) J. Biol. Chem. 268, 13947-13955); however, the @entity47295 mutant form of Rho, thought at the time to be wild type, was used in that work. The present results with @entity47295 Rho agree with the earlier work. C10 binding with mutant forms of Rho that are altered in RNA interactions, bearing @entity535 changes @entity70983 , @entity50449 , @entity70984 , @entity65127 , or @entity70985 , indicate that the higher affinity binding sites constitute what has been termed the primary RNA site, and the lower affinity sites constitute the secondary sites. The binding data together with the crystal structures for wild type Rho (Skordalakes, E., and Berger, J. M. (2003) Cell 114, 135-146) support structurally distinct locations on Rho for the two classes of C10-binding sites. The results are consistent with participation of residues 33 A apart in secondary site RNA interactions. The data further indicate that not all RNA sites on Rho must be filled for full @entity24427 and transcription termination activity, and suggest a model in which RNA binding to the higher affinity sites leads to a protein conformation change that exposes the previously hidden lower affinity sites.
