peptidoglycan

Information about peptidoglycan

Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid residues. Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. Some Archaea have a similar layer of pseudopeptidoglycan. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. A common misconception is that peptidoglycan gives the cell it's shape, however, while peptidoglycan helps maintain the structure of the cell, it is actually the MreB protein that facilitates cell shape. Peptidoglycan is also involved in binary fission during bacterial cell reproduction.^[1]

The peptidoglycan layer is substantially thicker in Gram-positive bacteria (20 to 80 nm) than in Gram-negative bacteria (7 to 8 nm), with the attachment of the S-layer. Peptidoglycan forms around 90% of the dry weight of Gram-positive bacteria but only 10% of Gram-negative strains. In Gram-positive strains, it is important in attachment roles and sterotyping purposes.^[2]

Antibiotic inhibition

Some antibacterial drugs such as penicillin interfere with the production of peptidoglycan by binding to bacterial enzymes known as penicillin-binding proteins or transpeptidases^[2]. Penicillin-binding proteins form the bonds between oligopeptide crosslinks in peptidoglycan. For a bacterial cell to reproduce through binary fission, more than a million peptidoglycan subunits (NAM-NAG+oligopeptide) must be attached to existing subunits.^[3] Mutations in transpeptidases that lead to reduced interactions with an antibiotic are a significant source of emerging antibiotic resistance.^[4]

Considered the human body's "own antibiotic", lysozymes found in tears work by breaking the β-(1,4)-glycosidic bonds in peptidoglycan (see below) and thereby destroying many bacterial cells. Antibiotics such as penicillin commonly target bacterial cell wall formation (of which peptidoglycan is an important component) because animal cells do not have cell walls.

Structure

The peptidoglycan layer in the bacterial cell wall is a crystal lattice structure formed from linear chains of two alternating amino sugars, namely N-acetyl glucosamine (GlcNAc or NAG) and N-acetyl muramic acid (MurNAc or NAM). The alternating sugars are connected by a β-(1,4)-glycosidic bond. Each MurNAc is attached to a short (4 to 5 residue) amino acid chain, normally containing D-alanine, D-glutamic acid and mesodiaminopimelic acid. These three amino acids do not occur in proteins and are thought to help protect against attacks by most peptidases. Cross-linking between amino acids in different linear amino sugar chains by an enzyme known as transpeptidase result in a 3-dimensional structure that is strong and rigid. The specific amino acid sequence and molecular structure vary with the bacterial species.^[5]

References

1. ^ Madigan M; Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0-13-144329-1.
2. ^ Salton MRJ, Kim KS (1996). Structure. In: Baron's Medical Microbiology (Barron S et al'', eds.), 4th ed., Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
3. ^ Bauman, R. (2007). Microbiology with Diseases by Taxonomy. Benjamin Cummings. ISBN 0-8053-7679-8.
4. ^ Spratt BG (1994). "Resistance to antibiotics mediated by target alterations". Science 264 (5157): 388-93. PMID 8153626.
5. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0-8385-8529-9.

External links

Diagrammatic representation of peptidoglycan structures.

• • [ e] Glycoproteins: mucoproteins
Haptoglobin - Intrinsic factor - Mucin (CD43, CD164) - Orosomucoid - Peptidoglycan - Phytohaemagglutinin

polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. The word is derived from the Greek, πολυ, polu, "many"; and μέρος, meros,
..... Click the link for more information.

Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.

Bacteria

Phyla

Actinobacteria
Aquificae
Chlamydiae
Bacteroidetes/Chlorobi
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Deinococcus-Thermus
Dictyoglomi
Fibrobacteres/Acidobacteria
Firmicutes
Fusobacteria
..... Click the link for more information.

Archaea
Woese, Kandler & Wheelis, 1990

Phyla

Crenarchaeota
Euryarchaeota
Korarchaeota
Nanoarchaeota
ARMAN
The Archaea (
..... Click the link for more information.

Pseudopeptidoglycan (also known as pseudomurein^[1]) is a major cell wall component of some archaebacteria that chemically differs from but morphologically, functionally, and structurally resembles eubacterial peptidoglycan.
..... Click the link for more information.

cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell.
..... Click the link for more information.

In biology, turgor pressure or turgidity is the pressure of the cell contents against the cell wall, in plant cells, determined by the water content of the vacuole, resulting from osmotic pressure. i.e.
..... Click the link for more information.

Cytoplasm is a gelatinous, semi-transparent fluid that fills most cells. Eukaryotic cells contain a nucleus that is kept separate from the cytoplasm by a double membrane layer. The cytoplasm has three major elements; the cytosol, organelles and inclusions.
..... Click the link for more information.

MreB is a protein found in bacteria that has been identified as a homologue of actin, as indicated by similarities in tertiary structure and conservation of active site peptide sequence.
..... Click the link for more information.

Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. This process results in the reproduction of a living cell by division into two equal or near-equal parts.
..... Click the link for more information.

Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.^[1] Gram-positive bacteria appear blue or violet under a microscope, while Gram-negative bacteria appear red or pink.
..... Click the link for more information.

1 nanometre =
SI units
010⁻⁹ m 010⁻³ μm
US customary / Imperial units
010⁻⁹ ft 010⁻⁹ in

A nanometre (American spelling: nanometer, symbol nm
..... Click the link for more information.

Gram-negative bacteria are those that do not retain crystal violet dye in the Gram staining protocol.^[1] Gram-positive bacteria will retain the dark blue dye after an alcohol wash.
..... Click the link for more information.

An S-layer (surface layer) is a part of the cell envelope commonly found in bacteria, as well as among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins.
..... Click the link for more information.

Penicillin (sometimes abbreviated PCN) is a group of beta-lactam antibiotics used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms.
..... Click the link for more information.

Penicillin binding proteins (PBPs) are a group of proteins which are characterized by their affinity for and binding of penicillin. They do not just bind penicillin but all beta-lactam antibiotics which are a family of antibiotics sharing a four membered lactam ring (beta-lactam
..... Click the link for more information.

Transpeptidase can refer to:

DD-transpeptidase
Another name for peptidyl transferase

..... Click the link for more information.

Antibiotic resistance is the ability of a microorganism to withstand the effects of an antibiotic. It is a specific type of drug resistance. Antibiotic resistance evolves naturally via natural selection through random mutation, but it could also be engineered.
..... Click the link for more information.

antibiotic is a chemotherapeutic agent that inhibits or abolishes the growth of micro-organisms, such as bacteria, fungi, or protozoans. The term originally referred to any agent with biological activity against living organisms; however, "antibiotic" now is used to refer to
..... Click the link for more information.

Lysozyme is a 14.4 kilodalton enzyme (EC 3.2.1.17 ) that damages bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins.
..... Click the link for more information.

crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a motif, a set of atoms arranged in a particular way, and a lattice. Motifs are located upon the points of a lattice, which is an array of points repeating periodically in three
..... Click the link for more information.

Sugars, brown
Nutritional value per 100 g (3.5 oz)
Energy 0 kcal 0 kJ

Carbohydrates 97.33 g
- Sugars 96.21 g
- Dietary fiber 0 g
Fat 0 g
Protein 0 g
Water 1.77 g
Thiamin (Vit. B1) 0.
..... Click the link for more information.

N-Acetylglucosamine (N-Acetyl-D-Glucosamine, or GlcNAc, or NAG) is a monosaccharide derivative of glucose. Chemically it is an amide between glucosamine and acetic acid.
..... Click the link for more information.

N-Acetylmuramic acid, or MurNAc, is the ether of lactic acid and N-acetylglucosamine with a chemical formula of C₁₁H₁₉NO₈. It is part of a biopolymer in the bacterial cell wall, built from alternating units of N-acetylglucosamine (GlcNAc)
..... Click the link for more information.

In chemistry, a glycosidic bond is a certain type of functional group that joins a carbohydrate (sugar) molecule to an alcohol, which may be another carbohydrate. Specifically, a glycosidic bond is formed between the hemiacetal group of a saccharide (or a molecule derived from a
..... Click the link for more information.

amino acid is a molecule that contains both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids with the general formula H₂NCHRCOOH, where R is an organic substituent.
..... Click the link for more information.

Cross-links are covalent bonds linking one polymer chain to another. They are the characteristic property of thermosetting polymer materials. In biology, cross-linking has applications in forming polyacrylamide gels for gel electrophoresis and in protein studies.
..... Click the link for more information.

This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.

EnglishInfo