|PROSITE documentation PDOC51714 [for PROSITE entry PS51714]|
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.
Bms1p and Tsr1p represent a new family of factors required for ribosome biogenesis. They are each independently required for 40S ribosomal subunit biogenesis. Bms1p, a protein required for pre-rRNA processing, contains an evolutionarily conserved G domain with five conserved polypeptide loops designated G1 through G5, which form contact sites with the guanine nucleotide or coordinate the Mg(2+) ion. Sequences ressembling G1 (consensus [GA]-x(4)-G-K-[ST]; also known as a P-loop), G4 (consensus [NT]-K-x-D), and G5 (consensus S-[AG] are present in all Bms1 proteins, and either fully conform with the consensus or contain, at most, single conservative substitutions. The G2 motif (consensus G-P-[IV]-T) contains a T residue involved in the coordination of the Mg(2+) required for GTP hydrolysis. The G3 motif diverges from the consensus found in G proteins, D-x(2)-G; however, the D residue is replaced with the conserved E residue. In contrast, Tsr1p lacks a P-loop and is not predicted to bind GTP. It functions at a later step of 40S ribosome production, possibly in assembly and/or export of 43S pre-ribosomal subunits to the cytosol [1,2,3].
The profile we developed covers the entire Bms1-type G domain.Last update:
April 2014 / First entry.
PROSITE method (with tools and information) covered by this documentation:
|1||Authors||Leipe D.D. Wolf Y.I. Koonin E.V. Aravind L.|
|Title||Classification and evolution of P-loop GTPases and related ATPases.|
|Source||J. Mol. Biol. 317:41-72(2002).|
|2||Authors||Wegierski T. Billy E. Nasr F. Filipowicz W.|
|Title||Bms1p, a G-domain-containing protein, associates with Rcl1p and is required for 18S rRNA biogenesis in yeast.|
|3||Authors||Gelperin D. Horton L. Beckman J. Hensold J. Lemmon S.K.|
|Title||Bms1p, a novel GTP-binding protein, and the related Tsr1p are required for distinct steps of 40S ribosome biogenesis in yeast.|