InterPro domain: IPR017453

This is a family of glycine cleavage H-proteins, part of the glycine cleavage system (GCS) found in bacteria, archaea, and the mitochondria of eukaryotes. GCS is a multienzyme complex consisting of 4 different components (P-, H-, T- and L-proteins) which catalyzes the oxidative cleavage of glycine [ 1 ]. The H-protein shuttles the methylamine group of glycine from the P-protein (glycine dehydrogenase) to the T-protein (aminomethyltransferase) via a lipoyl group, attached to a completely conserved lysine residue [ 2 ].

This entry represents the glycine cleavage system H protein. The genome of Aquifex aeolicus contains one protein belonging to this group, and four more related proteins not included here; it seems doubtful that all of these homologues are authentic H proteins. The Chlamydial homologue of the H protein is nearly as divergent as the Aquifex outgroup, is not accompanied by P and T proteins, and is not included in this entry.

1. The glycine decarboxylase system: a fascinating complex. Trends Plant Sci. 6, 167-76
2. X-ray structure determination at 2.6-A resolution of a lipoate-containing protein: the H-protein of the glycine decarboxylase complex from pea leaves. Proc. Natl. Acad. Sci. U.S.A. 91, 4850-3