Backbone chemical shift assignments of the glycine cleavage complex H protein of Escherichia coli.

Abstract

Glycine cleavage complex H protein (GcvH) is one of the four components that form the glycine cleavage complex (GCS), essential for the synthesis of C1 (one-carbon units) for cell metabolism, by the oxidative cleavage of glycine. The activity of this complex is induced in the presence of exogenous glycine, and is repressed by purines. GCS, in cooperation with GCA (serine hydroxymethyltransferase) regulates the endogenous levels of glycine and C1 units in the cell. GcvH, the lipoamide containing component of the complex, plays an indispensable role in this reaction, as its prosthetic group shuttles between the active site of the three other components of the GCS complex sequentially. In environments rich in exogenous lipoic acid, GcvH is converted to lipoyl-GcvH by Lipoate protein ligase (LplA), by the salvage pathway. When exogenous lipoic acid is deficient, it is post-translationally modified to lipoyl-GcvH by the consecutive action of two enzymes, (a) Lipoate protein ligase B (LipB) and (b) Lipoyl synthase (LipA). Although, the crystal structure has been determined for Escherichia coli GcvH, no information exists for its interaction with LipB or LipA. Therefore, we plan to study its interactions with the aforementioned enzymes. As a first step, we have carried out the complete backbone chemical shift assignments of the E. coli glycine cleavage complex H protein in its apo-form, as well as its C8- intermediate.