Structure and function of a chlorella virus-encoded glycosyltransferase
Ying Zhang1, Ye Xiang, James L Van Etten
1Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907, USA.
Structure (London, England : 1993)
|September 14, 2007
Summary
Paramecium bursaria chlorella virus-1 glycosyltransferase A64R selectively binds UDP-glucose. This finding clarifies the synthesis of viral glycans, crucial for understanding virus structure and function.
Area of Science:
- Virology
- Structural Biology
- Biochemistry
Background:
- Paramecium bursaria chlorella virus-1 (PBCV-1) encodes multiple glycosyltransferases.
- These enzymes are likely involved in synthesizing glycan components of the viral major capsid protein.
Purpose of the Study:
- To determine the substrate specificity of the PBCV-1 glycosyltransferase A64R.
- To elucidate the structural basis for A64R's enzymatic activity.
Main Methods:
- X-ray crystallography was used to determine the structure of A64R.
- Structures were solved for A64R complexed with UDP, CMP, GDP, and UDP-glucose in the presence of Mn(2+).
Main Results:
- A64R exhibits a mixed alpha/beta fold and binds UDP in the presence of Mn(2+).
- A64R selectively binds UDP-glucose, with significant conformational changes upon ligand binding.
- UDP-galactose and UDP-N-acetylglucosamine (UDP-GlcNAc) did not bind to A64R.
Conclusions:
- UDP-glucose is the most probable sugar donor for the A64R glycosyltransferase.
- The findings support the role of A64R in synthesizing glucose-containing glycans found on the PBCV-1 major capsid protein.
Related Concept Videos
00:56Viral Structure
Viruses are extraordinarily diverse in shape and size, but they all have several structural features in common. All viruses have a core that contains a DNA- or RNA-based genome. The core is surrounded by a protective coat of proteins called the capsid. The capsid is composed of subunits called capsomeres. The capsid and genome-containing core are together known as the nucleocapsid.
01:14Glycocalyx and its Functions
The glycocalyx is a carbohydrate-rich, fuzzy-appearing layer on the outer surface of the cell membrane. It is highly hydrophilic, because of this it attracts large amounts of water to the cell's surface. This aids the cell's interaction with the watery environment and also helps it to obtain substances dissolved in the water. It is also important for cell identification, self/non-self determination, and embryonic development and is used in cell-to-cell attachments to form tissues.
Components of...
Components of...
01:24Protein Transport to the Stroma
Chloroplasts are triple membrane structures with an outer membrane, an inner membrane, and a thylakoid membrane, each containing distinct metabolite transporters, membrane translocons, and enzymes. Appropriate sorting and translocating these proteins to their correct membrane systems is essential for chloroplast function.
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
01:11Protein Transport to the Outer Chloroplast Membrane
Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
01:18Protein Transport to the Inner Chloroplast Membrane
Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...
01:24Oligosaccharide Assembly
Protein glycosylation starts in the ER lumen and continues in the Golgi apparatus. Glycosyltransferases catalyze the addition of sugar molecules or glycosylation of proteins. Usually, these enzymes add sugars to the hydroxyl groups of selected serine or threonine residues to form O-linked glycans or the amino groups of asparagine residues to form N-linked glycans. Different positions on the same polypeptide chain can contain differently linked glycans.
Multiple sugar molecules that may or may...
Multiple sugar molecules that may or may...