Open AccessAn HflX-Type GTPase from Sulfolobus solfataricus Binds to the 50S Ribosomal Subunit in All Nucleotide-Bound States
Author(s) -
Fabian Blombach,
Hélène Launay,
Violeta Zorraquino,
Daan C. Swarts,
Lisa D. Cabrita,
Dario Benelli,
John Christodoulou,
Paola Londei,
John van der Oost
Publication year - 2011
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01552-10
Subject(s) - sulfolobus solfataricus , 50s , biology , ribosomal protein , eukaryotic large ribosomal subunit , ribosome , ribosomal rna , 30s , gtpase , eukaryotic small ribosomal subunit , eukaryotic ribosome , protein subunit , biochemistry , archaea , rna , gene
HflX GTPases are found in all three domains of life, the Bacteria, Archaea, and Eukarya. HflX from Escherichia coli has been shown to bind to the 50S ribosomal subunit in a nucleotide-dependent manner, and this interaction strongly stimulates its GTPase activity. We recently determined the structure of an HflX ortholog from the archaeon Sulfolobus solfataricus (SsoHflX). It revealed the presence of a novel HflX domain that might function in RNA binding and is linked to a canonical G domain. This domain arrangement is common to all archaeal, bacterial, and eukaryotic HflX GTPases. This paper shows that the archaeal SsoHflX, like its bacterial orthologs, binds to the 50S ribosomal subunit. This interaction does not depend on the presence of guanine nucleotides. The HflX domain is sufficient for ribosome interaction. Binding appears to be restricted to free 50S ribosomal subunits and does not occur with 70S ribosomes engaged in translation. The fingerprint (1)H-(15)N heteronuclear correlation nuclear magnetic resonance (NMR) spectrum of SsoHflX reveals a large number of well-resolved resonances that are broadened upon binding to the 50S ribosomal subunit. The GTPase activity of SsoHflX is stimulated by crude fractions of 50S ribosomal subunits, but this effect is lost with further high-salt purification of the 50S ribosomal subunits, suggesting that the stimulation depends on an extrinsic factor bound to the 50S ribosomal subunit. Our results reveal common properties but also marked differences between archaeal and bacterial HflX proteins.