Stirrup protein domain

In molecular biology, the Stirrup is a protein domain found only in the domain archaea, in prokaryotic protein ribonucleotide reductases. It obtains its name due to its resemblance to an old fashioned Japanese stirrup. Stirrip has a molecular mass of 9 kDa and is folded into an alpha/beta structure. It allows for binding of the reductase to DNA via electrostatic interactions, since it has a predominance of positive charges distributed on its surface.^[1]

Stirrup
crystal structure of an archaeal intein-encoded homing endonuclease pi-pfui
Identifiers
Symbol	Stirrup
Pfam	PF09061
InterPro	IPR015146
SCOP2	1dq3 / SCOPe / SUPFAM
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Function

This protein domain provides the precursors necessary for DNA synthesis. It catalyses the biosynthesis of DNA from RNA.^[2]

Structure

This structure contains a three-stranded beta-sheet to the solvent, which lies against alpha-helices.^[1]