The G-patch domain is an approximately 48 amino acid domain, which is found in a single copy in several RNA-associated proteins and in type D retroviral polyproteins. It is widespread among eukaryotes but is absent in archaea and bacteria. The G-patch domain has been called after its most notable feature, the presence of six highly conserved glycine residues. The position following the first conserved glycine is occupied almost invariably by an aromatic residue, and several other positions are occupied predominantly by either hydrophobic or small residues. Several groups of G-patch containing proteins are conserved in animals, plants and fungi. In some of these proteins the G-patch is the only recognizable domain but in most of them it is combined with other domains, which include well-defined RNA-binding domains, such as the RRM (see <PDOC00030>), dsRBD (see <PDOC50137>), SURP and R3H. It has been suggested that the G-patch domain has a specific function in RNA processing and, in particular, that it might be a previously undetected RNA-binding domain mediating a distinct type of RNA-protein interaction.

Secondary structure prediction indicates that the G-patch domain probably contains two α-helices, with four out of the six glycines located within an intervening loop.

Some proteins known to contain a G-patch domain are listed below:

• Eukaryotic 45-kDa splicing factor (SPF-45).
• Mammmalian SON protein, a DNA-binding protein.
• Human LUCA15, a multidomain RNA-binding protein that is the product of a gene deleted in certain lung tumors.
• Human DAN26/EPROT, a multidomain protein, which, in addition to the G-patch domain, contains an RNA polymerase II C-terminal repeat-binding domain seen in many proteins of the polyA-addition machinery.
• Arabidopsis thaliana DRT111, a protein which has been shown to partially restore recombination proficiency and DNA-damage resistance to E. coli mutants.
• Type D retroviral polyprotein, where the G-patch domain is found directly downstream of the protease domain (see <PDOC00128>).

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