A dominant negative mutant of the E. coli RNA helicase DbpA blocks assembly of the 50S ribosomal subunit

Lisa M. Sharpe Elles, Michael T. Sykes, James R. Williamson, Olke C Uhlenbeck*

*Corresponding author for this work

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

Escherichia coli DbpA is an ATP-dependent RNA helicase with specificity for hairpin 92 of 23S ribosomal RNA, an important part of the peptidyl transferase center. The R331A active site mutant of DbpA confers a dominant slow growth and cold sensitive phenotype when overexpressed in E. coli containing endogenous DbpA. Ribosome profiles from cells overexpressing DbpA R331A display increased levels of 50S and 30S subunits and decreased levels 70S ribosomes. Profiles run at low Mg2+ exhibit fewer 50S subunits and accumulate a 45S particle that contains incompletely processed and undermodified 23S rRNA in addition to reduced levels of several ribosomal proteins that bind late in the assembly pathway. Unlike mature 50S subunits, these 45S particles can stimulate the ATPase activity of DbpA, indicating that hairpin 92 has not yet been sequestered within the 50S subunit. Overexpression of the inactive DbpA R331A mutant appears to block assembly at a late stage when the peptidyl transferase center is formed, indicating a possible role for DbpA promoting this conformational change.

Original languageEnglish (US)
Pages (from-to)6503-6514
Number of pages12
JournalNucleic acids research
Volume37
Issue number19
DOIs
StatePublished - Nov 16 2009

ASJC Scopus subject areas

  • Genetics

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