Related Experiment Video
Updated: Jun 14, 2026
09:09
Semi-Quantitative Analysis of Peptidoglycan by Liquid Chromatography Mass Spectrometry and Bioinformatics
Published on: October 13, 2020
Molecular basis for peptidoglycan recognition by a bactericidal lectin.
Rebecca E Lehotzky1, Carrie L Partch, Sohini Mukherjee
1Departments of Immunology, The Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Summary
RegIII proteins like HIP/PAP kill gut bacteria by binding peptidoglycan. This study reveals HIP/PAP uses a unique calcium-independent mechanism for bacterial cell wall recognition.
Area of Science:
- Microbiology
- Structural Biology
- Immunology
Background:
- RegIII proteins are secreted C-type lectins crucial for gut antimicrobial defense against Gram-positive bacteria.
- These lectins interact with bacterial cell wall peptidoglycan but lack typical calcium-dependent carbohydrate-binding sequences.
Purpose of the Study:
- To elucidate the molecular mechanism of peptidoglycan recognition by the human RegIII lectin, HIP/PAP.
- To investigate the role of the EPN motif in HIP/PAP's calcium-independent binding and bacterial killing.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed to determine the structure and binding interactions of HIP/PAP with peptidoglycan.
- Analysis of the EPN motif's function in calcium-dependent and independent carbohydrate binding.
Main Results:
- HIP/PAP recognizes the peptidoglycan carbohydrate backbone independently of calcium, utilizing a conserved EPN motif essential for antibacterial activity.
- The EPN motif in HIP/PAP functions uniquely, supporting calcium-independent carbohydrate binding.
- HIP/PAP binding affinity is influenced by carbohydrate ligand length, suggesting a 'bind and jump' mechanism along peptidoglycan chains.
Conclusions:
- The EPN motif is a versatile functional module capable of both calcium-dependent and independent carbohydrate binding.
- HIP/PAP employs a dynamic 'bind and jump' mechanism for high-affinity interaction with clustered carbohydrate epitopes on bacterial peptidoglycan.
- This mechanism is vital for effective antimicrobial protection in the mammalian gut.
Related Concept Videos
01:23Inhibitors of Gram-positive Cell Wall Synthesis
Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains cell shape. The synthesis of peptidoglycan is a crucial process in bacterial growth and serves as a primary target for many antibiotics.Mechanism of Action of Beta-Lactam AntibioticsBeta-lactam antibiotics, such as penicillin, inhibit peptidoglycan synthesis in actively growing cells. These antibiotics share a characteristic four-membered...
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...
01:28Peptidoglycan Synthesis
Structure of PeptidoglycanPeptidoglycan is a vital structural component of the bacterial cell wall, providing mechanical strength and shape to the cell. It consists of repeating units of two sugars—N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)—linked by β-1,4 glycosidic bonds. These sugar chains are cross-linked by short peptide chains, forming a mesh-like polymer that surrounds the bacterial plasma membrane.Cytoplasmic Phase – Precursor SynthesisPeptidoglycan biosynthesis begins in...
01:22Bacterial Cell Wall
The bacterial cell wall is an essential structural component that encases the plasma membrane, preserving cellular integrity, determining shape, and protecting against osmotic stress. This rigid yet flexible structure primarily comprises peptidoglycan, a polymer that forms a mesh-like matrix conferring mechanical strength and flexibility.Peptidoglycan Composition and StructurePeptidoglycan, the core of the bacterial cell wall, comprises alternating units of N-acetylglucosamine (NAG) and...
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...
01:12Bacterial Toxins
Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...