PTS Lactose-N,N'-Diacetylchitobiose Family

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The PTS Lactose-N,N’-Diacetylchitobiose (Lac) Family (TC# 4.A.3) includes several sequenced lactose porters of Gram-positive bacteria, as well as the Escherichia coli and Borrelia burgdorferi N,N'-diacetylchitobiose (Chb) porters. [1] [2] It is part of the PTS-GFL superfamily. The former can transport aromatic β-glucosides and cellobiose, as well as Chb. However, only Chb induces expression of the chb operon.

Lactose chemical compound

Lactose is a disaccharide. It is a sugar composed of galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by weight). The name comes from lac (gen. lactis), the Latin word for milk, plus the suffix -ose used to name sugars. The compound is a white, water-soluble, non-hygroscopic solid with a mildly sweet taste. It is used in the food industry.

Gram-positive bacteria bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall

Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.

<i>Escherichia coli</i> species of Gram-negative, rod-shaped bacterium

Escherichia coli, also known as E. coli, is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination. The harmless strains are part of the normal microbiota of the gut, and can benefit their hosts by producing vitamin K2, and preventing colonization of the intestine with pathogenic bacteria, having a symbiotic relationship. E. coli is expelled into the environment within fecal matter. The bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly afterwards.

Contents

Structure

While the Lac porters consist of two polypeptide chains (IIA and IICB), the Chb porters of E. coli and B. burgdorferi consist of three (IIA, IIB and IIC). In E. coli, the IIAChb protein has been shown to form a stable dimer both when phosphorylated and when unphosphorylated. The IIC domains of these permeases are believed to have a uniform topology with 8 TMSs. [3]

Lac porters in E. coli

In E. coli, the IIBChb is a monomer. Two IIBChb monomers associate with the IIAChb dimer. The structure of the IIB domain of the Chb porter has been determined both by NMR and by X-ray crystallography. It exhibits an α/β doubly wound superfold. This is different from the structure of the IIBGlc and IIBMandomains. IIBSgc, believed to function in pentose transport, is homologous to IIBLac and IIBChb. In Bacillus cereus, the crystal structure of the Chb protein is known. [4] The IIC domains of members of the Lac family are all more similar to each other than they are to those of the Glc, Bgl, Fru and Mtl families.

Nuclear magnetic resonance spectroscopic technique relying on the energy difference between the quantum spin states of electrons when exposed to an external magnetic field

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong static magnetic field are perturbed by a weak oscillating magnetic field and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. Nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics, crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI).

X-ray crystallography Technique used in studying crystal structure

X-ray crystallography (XRC) is a technique used for determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information.

<i>Bacillus cereus</i> species of bacterium

Bacillus cereus is a Gram-positive, rod-shaped, facultatively anaerobic, motile, beta-hemolytic, spore forming, bacterium commonly found in soil and food. Some strains are harmful to humans and cause foodborne illness, while other strains can be beneficial as probiotics for animals. The bacteria is classically contracted from fried rice dishes that have been sitting at room temperature for hours. B. cereus bacteria are facultative anaerobes, and like other members of the genus Bacillus, can produce protective endospores. Its virulence factors include cereolysin and phospholipase C.

Related Research Articles

Beta-galactosidase hydrolase enzyme

β-galactosidase, also called lactase, beta-gal or β-gal, is a glycoside hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides through the breaking of a glycosidic bond. β-galactosides include carbohydrates containing galactose where the glycosidic bond lies above the galactose molecule. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins.

Mannose chemical compound

Mannose, packaged as the nutritional supplement "d-mannose", is a sugar monomer of the aldohexose series of carbohydrates. Mannose is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation are associated with mutations in enzymes involved in mannose metabolism.

<i>lac</i> operon Set genes encoding proteins and enzymes for lactose metabolism

The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and many other enteric bacteria. Although glucose is the preferred carbon source for most bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of beta-galactosidase. Gene regulation of the lac operon was the first genetic regulatory mechanism to be understood clearly, so it has become a foremost example of prokaryotic gene regulation. It is often discussed in introductory molecular and cellular biology classes for this reason. This lactose metabolism system was used by François Jacob and Jacques Monod to determine how a biological cell knows which enzyme to synthesize. Their work on the lac operon won them the Nobel Prize in Physiology in 1965.

PEP group translocation, also known as the phosphotransferase system or PTS, is a distinct method used by bacteria for sugar uptake where the source of energy is from phosphoenolpyruvate (PEP). It is known as multicomponent system that always involves enzymes of the plasma membrane and those in the cytoplasm. The PTS system uses active transport. After the translocation across the membrane, the metabolites transported are modified. The system was discovered by Saul Roseman in 1964. The bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) transports and phosphorylates its sugar substrates in a single energy-coupled step. This transport process is dependent on several cytoplasmic phosphoryl transfer proteins - Enzyme I (I), HPr, Enzyme IIA (IIA), and Enzyme IIB (IIB)) as well as the integral membrane sugar permease (IIC).The PTS Enzyme II complexes are derived from independently evolving 4 PTS Enzyme II complex superfamilies, that include the (1) Glucose (Glc),(2) Mannose (Man), (3) Ascorbate-Galactitol (Asc-Gat) and (4) Dihydroxyacetone (Dha) superfamilies.

Isopropyl β-<small>D</small>-1-thiogalactopyranoside chemical compound

Isopropyl β-D-1-thiogalactopyranoside (IPTG) is a molecular biology reagent. This compound is a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lac operon, and it is therefore used to induce protein expression where the gene is under the control of the lac operator.

The permeases are membrane transport proteins, a class of multipass transmembrane proteins that allow the diffusion of a specific molecule in or out of the cell in the direction of a concentration gradient, a form of facilitated diffusion.

Beta-galactoside permease

Galactoside permease is a protein coded by the lacY gene of the lac operon, and is found bound to the membrane of a cell for the purpose of binding galactoside molecules that have been solubilized. The protein is part of a system whose main function is to catalyze the accumulation and transport of lactose and other beta-galactosides across the permeable barrier of a membrane.

Blue–white screen

The blue–white screen is a screening technique that allows for the rapid and convenient detection of recombinant bacteria in vector-based molecular cloning experiments. DNA of interest is ligated into a vector. The vector is then inserted into a competent host cell viable for transformation, which are then grown in the presence of X-gal. Cells transformed with vectors containing recombinant DNA will produce white colonies; cells transformed with non-recombinant plasmids grow into blue colonies. This method of screening is usually performed using a suitable bacterial strain, but other organisms such as yeast may also be used.

Virulence-related outer membrane protein family InterPro Family

Virulence-related outer membrane proteins are expressed in Gram-negative bacteria and are essential to bacterial survival within macrophages and for eukaryotic cell invasion.

Lactose permease

Lactose permease is a membrane protein which is a member of the major facilitator superfamily. Lactose permease can be classified as a symporter, which uses the proton gradient towards the cell to transport β-galactosides such as lactose in the same direction into the cell.

Saccharide transporter

The bacterial phosphoenolpyruvate: sugar phosphotransferase system (PTS) is a multi-protein system involved in the regulation of a variety of metabolic and transcriptional processes. The PTS catalyzes the phosphorylation of incoming sugar substrates concomitant with their translocation across the cell membrane. The general mechanism of the PTS is the following: a phosphoryl group from phosphoenolpyruvate (PEP) is transferred to enzyme-I (EI) of PTS which in turn transfers it to a phosphoryl carrier protein (HPr). Phospho-HPr then transfers the phosphoryl group to a sugar-specific permease which consists of at least three structurally distinct domains which can either be fused together in a single polypeptide chain or exist as two or three interactive chains, formerly called enzymes II (EII) and III (EIII). The IIC domain catalyzes the transfer of a phosphoryl group from IIB to the sugar substrate.

Howard Ronald Kaback is an American Biochemist, known for Kabackosomes, the cell-free membrane transport vesicles. He is the brother of Michael M. Kaback, pediatrician and human geneticist, who developed a screening program to detect and prevent Tay–Sachs disease, a rare and fatal genetic disorder most common in Ashkenazi Jews.

The phosphotransferases system (PTS-GFL) superfamily is a superfamily of phosphotransferase enzymes that facilitate the transport of glucose, glucitol (G), fructose (F) and lactose (L). Classification has been established through phylogenic analysis and bioinformatics.

The PTSGlucose-Glucoside (Glc) family includes porters specific for glucose, glucosamine, N-acetylglucosamine and a large variety of α- and β-glucosides, and is part of the PTS-GFL superfamily.

The PTS Fructose-Mannitol (Fru) Family is a large and complex family that is part of the PTS-GFL superfamily. It includes several sequenced fructose, mannose and mannitol-specific porters, as well as several putative PTS porters of unknown specificities. The fructose porters of this family phosphorylate fructose on the 1-position. Those of TC family 4.A.6 phosphorylate fructose on the 6-position.

The PTS Glucitol (Gut) Family consists only of glucitol-specific porters, but these occur both in Gram-negative and Gram-positive bacteria. It is part of the PTS-GFL superfamily.

Permease of phosphotransferase system is a superfamily of phosphotransferase enzymes that facilitate the transport of L-ascorbate (A) and galactitol (G). Classification has been established through phylogenic analysis and bioinformatics.

The PTS Galactitol (Gat) Family is part of the PTS-AG superfamily. The biochemistry of this family is poorly defined. The only well-characterized member of this family is the galactitol permease of Escherichia coli. However, a homologous IIC protein from Listeria monocytogenes has been shown to be required for D-arabitol fermentation. It presumably functions together with IIAGat and IIBGat homologues. IICGat is distantly related to IICSgc of E. coli; IIAGat is distantly related to IIASga and IIASgcof E. coli as well as IIAMtl and IIAFru. IIBGat is distantly related to IIBSga and IIBSgc of E. coli. Domains in the LicR/CelR family of transcriptional activators show C-terminal domains exhibiting weak sequence similarity to IIBGat and IIAGat.

The PTS L-Ascorbate (L-Asc) Family includes porters specific for L-ascorbate, and is part of the PTS-AG superfamily. A single PTS permease of the L-Asc family of PTS permeases has been functionally characterized. This is the SgaTBA system, renamed UlaABC by Yew and Gerlt.

The PTS Mannose-Fructose-Sorbose (Man) Family is a group of multicomponent PTS systems that are involved in sugar uptake in bacteria. This transport process is dependent on several cytoplasmic phosphoryl transfer proteins - Enzyme I (I), HPr, Enzyme IIA (IIA), and Enzyme IIB (IIB) as well as the integral membrane sugar permease complex (IICD). It is not part of the PTS-AG or PTS-GFL superfamilies.

References

  1. ↑ Keyhani, N. O.; Bacia, K.; Roseman, S. (2000-10-20). "The transport/phosphorylation of N,N'-diacetylchitobiose in Escherichia coli. Characterization of phospho-IIB(Chb) and of a potential transition state analogue in the phosphotransfer reaction between the proteins IIA(Chb) AND IIB(Chb)". The Journal of Biological Chemistry. 275 (42): 33102–33109. doi:10.1074/jbc.M001045200. ISSN   0021-9258. PMID   10913119.
  2. ↑ Tilly, K.; Elias, A. F.; Errett, J.; Fischer, E.; Iyer, R.; Schwartz, I.; Bono, J. L.; Rosa, P. (2001-10-01). "Genetics and regulation of chitobiose utilization in Borrelia burgdorferi". Journal of Bacteriology. 183 (19): 5544–5553. doi:10.1128/JB.183.19.5544-5553.2001. ISSN   0021-9193. PMC   95445  Lock-green.svg. PMID   11544216.
  3. ↑ Nguyen, Thai X.; Yen, Ming-Ren; Barabote, Ravi D.; Saier, Milton H. (2006-01-01). "Topological predictions for integral membrane permeases of the phosphoenolpyruvate:sugar phosphotransferase system". Journal of Molecular Microbiology and Biotechnology. 11 (6): 345–360. doi:10.1159/000095636. ISSN   1464-1801. PMID   17114898.
  4. ↑ Cao, Yu; Jin, Xiangshu; Levin, Elena J.; Huang, Hua; Zong, Yinong; Quick, Matthias; Weng, Jun; Pan, Yaping; Love, James (2011-05-05). "Crystal structure of a phosphorylation-coupled saccharide transporter". Nature. 473 (7345): 50–54. doi:10.1038/nature09939. ISSN   1476-4687. PMC   3201810  Lock-green.svg. PMID   21471968.

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