Related Experiment Video
Updated: Aug 13, 2026
10:13
Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
Published on: August 11, 2018
Subcellular localization of the Streptococcus mutans P1 protein C terminus
M K Homonylo-McGavin1, S F Lee, G H Bowden
1Department of Oral Biology, Faculty of Dentistry, University of Manitoba, Winnipeg, Canada.
Canadian Journal of Microbiology
|August 24, 1999
Summary
The Streptococcus mutans P1 protein
Area of Science:
- Microbiology
- Molecular Biology
- Cell Biology
Background:
- Streptococcus mutans is a key pathogen in dental caries.
- The P1 protein's role and localization are crucial for understanding its function.
- Previous studies have not precisely defined the P1 protein's C-terminal anchor location.
Purpose of the Study:
- To ascertain the subcellular localization of the Streptococcus mutans P1 protein's C-terminal anchor.
- To investigate the association of the P1 protein with cell wall components, particularly peptidoglycan.
Main Methods:
- Cell envelope fractionation of Streptococcus mutans.
- Western immunoblotting using specific monoclonal (MAb 6-8C) and polyclonal (anti-P1COOH) antibodies.
- Enzymatic (mutanolysin) and chemical (trichloroacetic acid) treatments of cell wall components.
Main Results:
- Monoclonal antibody detected P1 protein in cell walls, but not membranes.
- Polyclonal antibody against P1 C-terminus (P1COOH) only recognized P1 after mutanolysin treatment of cell walls, indicating epitope masking by peptidoglycan.
- P1 protein was exclusively associated with peptidoglycan, not cell-wall-associated carbohydrates.
Conclusions:
- The C-terminal 144 amino acids of the P1 protein are embedded within the Streptococcus mutans cell wall.
- P1 protein is tightly associated with peptidoglycan, suggesting intercalation within the peptidoglycan strands.
- The localization implies a structural role for P1 protein within the bacterial cell wall.
Related Concept Videos
01:34Protein Transport into the Inner Mitochondrial Membrane
Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Transport of mitochondrial precursors across the TIM23 channel is driven by...
01:26Insertion of Single-pass Transmembrane Proteins in the RER
Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
01:29GPI Anchoring of Proteins in the ER Membrane
GPI-anchoring is a post-translational, reversible protein modification that is ubiquitous in eukaryotes. Such proteins are primarily present on the exoplasmic leaflet of the plasma membrane.
GPI-anchor structure
A sequence of 11 enzymatic reactions results in the synthesis of the complete GPI anchor consisting of a hydrophobic and a hydrophilic portion. The hydrophobic portion comprises phosphatidylinositol, while the hydrophilic part comprises polar groups like phosphoethanolamine,...
GPI-anchor structure
A sequence of 11 enzymatic reactions results in the synthesis of the complete GPI anchor consisting of a hydrophobic and a hydrophilic portion. The hydrophobic portion comprises phosphatidylinositol, while the hydrophilic part comprises polar groups like phosphoethanolamine,...
01:21Structure of Porins
Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...
01:19Formation of Lipopolysaccharides
Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
01:26Bacterial Translocation and Protein Secretion
Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...