Related Experiment Video
Updated: Aug 4, 2026
09:40
Phage Phenomics: Physiological Approaches to Characterize Novel Viral Proteins
Published on: June 11, 2015
Structure and function of a novel coliphage-associated sialidase
Y Machida1, K Miyake, K Hattori
1Department of Biotechnology, Graduate School of Bioengineering, Nagoya University, Chikusa-ku, Nagoya, Japan.
FEMS Microbiology Letters
|January 6, 2000
Summary
Coliphage 63D contains sialidase enzyme in its tail plate. This enzyme comprises four identical subunits, cross-linked by disulfide bonds, forming a hexagonal array.
Area of Science:
- Microbiology
- Virology
- Enzymology
Background:
- Coliphages are viruses that infect bacteria.
- Sialidases are enzymes that cleave sialic acids.
- The localization of enzymes within phage particles is crucial for understanding phage-bacterial interactions.
Purpose of the Study:
- To determine the precise location of the sialidase enzyme within the 63D coliphage particle.
- To characterize the structure and composition of the sialidase enzyme.
Main Methods:
- Partial destruction of coliphages by sonication.
- Size fractionation of disrupted phage particles using sucrose density gradients.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for molecular mass determination.
- Enzyme assays to confirm sialidase activity.
- Electron microscopy for structural visualization.
Main Results:
- The sialidase enzyme is localized in the tail plate of the 63D coliphage.
- The enzyme is composed of four identical subunits.
- Each subunit has a molecular mass of 90 kDa.
- Subunit assembly is stabilized by disulfide bonds.
- Six enzyme molecules form a hexagonal array in the phage tail plate.
Conclusions:
- The sialidase enzyme is an integral component of the 63D coliphage tail structure.
- The specific arrangement of sialidase subunits suggests a functional role in bacterial cell surface interaction or lysis.
- This finding provides insights into the molecular mechanisms of phage-bacterial interactions.
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.
01:30Lytic Cycle of Bacteriophages
Bacteriophages, also known as phages, are specialized viruses that infect bacteria. A key characteristic of phages is their distinctive “head-tail” morphology. A phage begins the infection process (i.e., lytic cycle) by attaching to the outside of a bacterial cell. Attachment is accomplished via proteins in the phage tail that bind to specific receptor proteins on the outer surface of the bacterium. The tail injects the phage’s DNA genome into the bacterial cytoplasm. In the lytic replication...
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...
01:20Viral Replication: Lytic Cycle
Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized lytic replication cycle in Escherichia coli (E. coli). This process ensures the rapid proliferation of the virus while ultimately leading to the destruction of the bacterial host.Attachment and DNA InjectionThe infection process begins with the recognition and binding of the T4 phage to the E. coli cell surface. Tail fibers of the phage...
01:20Determinants of Bacterial Pathogenicity and Virulence
Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...
01:25Inhibitors Of Virion Release
Viral replication and dissemination rely on efficient mechanisms for host cell entry, genome replication, assembly, and release. Influenza viruses, such as types A and B, are negative-sense single-stranded RNA viruses with a segmented genome, that depend on two critical surface glycoproteins to carry out these processes: hemagglutinin (HA) and neuraminidase (NA). HA initiates infection by binding to sialic acid residues on the surface of host epithelial cells, facilitating receptor-mediated...