title: 14 Modification of glutamine residues in proteins involved in translation.
abstract: The only known protein glutamine methylations take place on proteins related to the ribosomal function. The modification is a mono-methylation on the side-chain amide nitrogen (N5). The glutamine residue within a Gly-Gly-Gln (GGQ) motif of the polypeptide release factor (RF) is methylated, and the modification is involved in polypeptide chain termination. A defect in RF methylation results in a dramatic growth defect and substantial read-through of stop codons during translation. Ribosomal protein L3 is also methylated on a glutamine residue. This modification is only found in bacteria and is not essential, but may be involved in efficient assembly of the ribosome structure. Gin methyltransferases (MTase) adopt the canonical class I MTase structure and contain a [D/N]PPY motif to position the substrate and facilitate catalysis. This motif was previously only thought to function in DNA N-MTases, but has been shown to act more generally on neutral planar amidesubstrates.
authors.affiliation: Department of Biochemistry University of Utah 15 North Medical DriveEast Salt Lake City, UT 84112, USA.
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Schubert