PROSITE documentation PDOC51705
HflX-type guanine nucleotide-binding (G) domain profile


The P-loop (see <PDOC00017>) guanosine triphosphatases (GTPases) control a multitude of biological processes, ranging from cell division, cell cycling, and signal transduction, to ribosome assembly and protein synthesis. GTPases exert their control by interchanging between an inactive GDP-bound state and an active GTP-bound state, thereby acting as molecular switches. The common denominator of GTPases is the highly conserved guanine nucleotide-binding (G) domain that is responsible for binding and hydrolysis of guanine nucleotides [1,2,3].

Within the translation factor-related (TRAFAC) class of P-loop GTPases, the HflX-type is a widely distributed family of GTPases that interact with the large ribosomal subunit. The broad phylogenetic distribution pattern of HflX GTPases in Bacteria, Archaea, and Eukaryotes (including human) suggests a basic cellular function for this protein family.

The HflX-type G domain is composed of six β-strands and five α-helices (see <PDB:2QTF>) [2]. It consists of the following conserved sequence motifs: the G1 motif (or P-loop), consensus GX4GK(S/T), which is responsible for interacting with the α and β-phosphates of nucleotide di- and triphosphates; the G2 variable effector loop (DXnT); the G3 motif (DX2G), which interacts with the γ-phosphate of nucleotide triphosphates; and the G4 motif (NKXD), which conveys specificity for guanine nucleotides through hydrogen bonding to the base [3].

The profile we developed covers the entire HflX-type G domain.

Last update:

February 2014 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

G_HFLX, PS51705; HflX-type guanine nucleotide-binding (G) domain profile  (MATRIX)


1AuthorsLeipe D.D. Wolf Y.I. Koonin E.V. Aravind L.
TitleClassification and evolution of P-loop GTPases and related ATPases.
SourceJ. Mol. Biol. 317:41-72(2002).
PubMed ID11916378

2AuthorsWu H. Sun L. Blombach F. Brouns S.J.J Snijders A.P.L: Lorenzen K. van den Heuvel R.H.H. Heck A.J.R. Fu S. Li X. Zhang X.C. Rao Z. van der Oost J.
TitleStructure of the ribosome associating GTPase HflX.
SourceProteins 78:705-713(2010).
PubMed ID19787775

3AuthorsShields M.J. Fischer J.J. Wieden H.-J.
TitleToward understanding the function of the universally conserved GTPase HflX from Escherichia coli: a kinetic approach.
SourceBiochemistry 48:10793-10802(2009).
PubMed ID19824612

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