3EWI: Structural Analysis Of The C-terminal Domain Of Murine Cmp-sialic Acid Synthetase

The biosynthesis of sialic acid-containing glycoconjugates is crucial for the development of vertebrate life. Cytidine monophosphate-sialic acid synthetase (CSS) catalyzes the metabolic activation of sialic acids. In vertebrates, the enzyme is chimeric, with the N-terminal domain harboring the synthetase activity. The function of the highly conserved C-terminal domain (CSS-CT) is unknown. To shed light on its biological function, we solved the X-ray structure of murine CSS-CT to 1.9 A resolution. CSS-CT is a stable shamrock-like tetramer that superimposes well with phosphatases of the haloacid dehalogenase superfamily. However, a region found exclusively in vertebrate CSS-CT appears to block the active-site entrance. Accordingly, no phosphatase activity was observed in vitro, which points toward a nonenzymatic function of CSS-CT. A computational three-dimensional model of full-length CSS, in combination with in vitro oligomerization studies, provides evidence that CSS-CT serves as a platform for the quaternary organization governing the kinetic properties of the physiologically active enzyme as demonstrated in kinetic studies.
PDB ID: 3EWIDownload
MMDB ID: 76065
PDB Deposition Date: 2008/10/15
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 3EWI: tetrameric; determined by author and by software (PISA)
Molecular Components in 3EWI
Label Count Molecule
Proteins (4 molecules)
N-acylneuraminate Cytidylyltransferase(Gene symbol: Cmas)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB