Running in reverse: the structural basis for translocation polarity in hexameric helicases.

ABSTRACT: Hexameric helicases couple ATP hydrolysis to processive separation of nucleic acid duplexes, a process critical for gene expression, DNA replication, and repair. All hexameric helicases fall into two families with opposing translocation polarities: the 3'-->5' AAA+ and 5'-->3' RecA-like enzymes. To understand how a RecA-like hexameric helicase engages and translocates along substrate, we determined the structure of the E. coli Rho transcription termination factor bound to RNA and nucleotide. Interior nucleic acid-binding elements spiral around six bases of RNA in a manner unexpectedly reminiscent of an AAA+ helicase, the papillomavirus E1 protein. Four distinct ATP-binding states, representing potential catalytic intermediates, are coupled to RNA positioning through a complex allosteric ne

SUBMITTER: Thomsen ND 

PROVIDER: S-EPMC2772833 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature