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why do cells need carrier proteins that transport glucose

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Sugar_tr
Identifiers
Symbolization Sugar_tr
Pfam PF00083
Pfam clan CL0015
InterPro IPR005828
PROSITE PDOC00190
TCDB 2.A.1.1
OPM superfamily 15
OPM protein 4gc0

Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose across the plasma tissue layer, a summons titled facilitated diffusion. Because glucose is a vital source of energy for all life, these transporters are present altogether phyla. The GLUT or SLC2A home are a protein fellowship that is found in most class cells. 14 GLUTS are encoded by hominian genome. GLUT is a eccentric of uniporter transporter protein.

Synthesis of free glucose [edit out]

All but non-autotrophic cells are unable to make free glucose because they lack expression of glucose-6-phosphatase and, thus, are involved only in glucose uptake and catabolism. Usually produced only in hepatocytes, in fasting conditions, other tissues such as the intestines, muscles, brain, and kidneys are able-bodied to produce glucose following activation of gluconeogenesis.

Glucose transport in yeast [edit]

In Saccharomyces cerevisiae glucose transport takes place through facilitated diffusion.[1] The transport proteins are mainly from the Hxt sept, but many other transporters have been identified.[2]

Name Properties Notes
Snf3 low-glucose sensor; repressed by glucose; low look level; repressor of Hxt6
Rgt2 high-glucose sensor; low expression layer
Hxt1 Kilometer: 100 mM,[3] 129 - 107 mM[1] low-phylogenetic relation glucose transporter; evoked by high glucose level
Hxt2 Km = 1.5[1] - 10 mM[3] alto/halfway-affinityglucose transporter; induced by low glucose level[3]
Hxt3 Vm = 18.5, Kd = 0.078, Kilometer = 28.6/34.2[1] - 60 mM[3] low-affinity glucose transporter[3]
Hxt4 Vm = 12.0, Kd = 0.049, Klick = 6.2[1] intermediate-affinity glucose transporter[3]
Hxt5 Km = 10 mM[4] Cautious glucose affinity. Abundant during stationary phase, sporulation and low glucose conditions. Transcription inhibited by glucose.[4]
Hxt6 Vm = 11.4, Kd = 0.029, Km = 0.9/14,[1] 1.5 millimetre[3] high glucose affinity[3]
Hxt7 Vm = 11.7, Kd = 0.039, Km = 1.3, 1.9,[1] 1.5 mM[3] alto glucose phylogenetic relation[3]
Hxt8 low expression level[3]
Hxt9 involved in pleiotropic drug resistance[3]
Hxt11 knotty in pleiotropic drug resistance[3]
Gal2 Vm = 17.5, Kd = 0.043, Km = 1.5, 1.6[1] high brain sugar affinity[3]

Glucose transport in mammals [edit out]

GLUTs are integral membrane proteins that contain 12 tissue layer-spanning helices with both the amino and carboxylic termini unclothed on the cytoplasmic side of the plasma tissue layer. GLUT proteins transport glucose and coreferent hexoses according to a exemplar of alternate conformation,[5] [6] [7] which predicts that the transporter exposes a single substrate binding site toward either the outside or the inside of the cell. Binding of glucose to one situation provokes a conformational change associated with send, and releases glucose to the other side of the membrane. The inner and external glucose-binding sites are, it seems, located in transmembrane segments 9, 10, 11;[8] also, the DLS motif located in the seventh transmembrane segment could be involved in the choice and affinity of transported substrate.[9] [10]

Types [edit]

Apiece glucose transporter isoform plays a specific role in glucose metabolic process determined aside its practice of tissue expression, substrate specificity, send off kinetics, and orderly verbalism in different physiologic conditions.[11] Up to now, 14 members of the GLUT/SLC2 birth been identified.[12] On the foundation of sequence similarities, the GLUT family has been divided into three subclasses.

Class I [redact]

Class I comprises the well-characterised glucose transporters GLUT1-GLUT4.[13]

Name Distribution Notes
GLUT1 Is cosmopolitan in fetal tissues. In the adult, information technology is expressed at highest levels in erythrocytes and besides in the endothelial cells of roadblock tissues such as the blood–nous barrier. However, IT is responsible for the David Low level of basal glucose intake required to sustain respiration all told cells. Levels in cell membranes are increased aside reduced glucose levels and decreased by hyperbolic glucose levels. GLUT1 construction is upregulated in many tumors.
GLUT2 Is a duplex conveyer belt, allowing glucose to menstruum in 2 directions. Is expressed past renal tubular cells, colorful cells and pancreatic beta cells. It is also present in the basolateral tissue layer of the small intestine epithelium. Bidirectionality is required in liver cells to uptake glucose for glycolysis and glycogenesis, and release of glucose during gluconeogenesis. In pancreatic beta cells, free flowing glucose is required so that the intracellular environment of these cells crapper accurately gauge the serum glucose levels. All three monosaccharides (glucose, galactose, and fructose) are transported from the intestinal mucosal cubicle into the portal circulation by GLUT2. Is a high pressure-frequency and low-affinity isoform.[12]
GLUT3 Express mostly in neurons (where it is believed to equal the main glucose transporter isoform), and in the placenta. Is a high-affinity isoform, allowing IT to transport even in times of down glucose concentrations.
GLUT4 Expressed in adipose tissues and striated muscle (skeletal heftines and cardiac muscle). Is the insulin-regulated glucose transporter. Responsible for insulin-thermostated glucose storage.
GLUT14 Expressed in testes similarity to GLUT3 [12]

Classes II/III [edit]

Class II comprises:

  • GLUT5 (SLC2A5), a fructose conveyer in enterocytes
  • GLUT7 (SLC2A7), found in the small and large intestine,[12] transporting glucose out of the endoplasmic reticulum[14]
  • GLUT9 - (SLC2A9)
  • GLUT11 (SLC2A11)

Sort out III comprises:

  • GLUT6 (SLC2A6),
  • GLUT8 (SLC2A8),
  • GLUT10 (SLC2A10),
  • GLUT12 (SLC2A12), and
  • GLUT13, also H+/myo-inositol transporter HMIT (SLC2A13), in the first place denotative in brain.[12]

Almost members of classes II and III have been identified recently in homology searches of Eastern Standard Time databases and the sequence information provided by the various genome projects.

The function of these new glucose transporter isoforms is still not clearly defined at present. Respective of them (GLUT6, GLUT8) are made of motifs that serve retain them intracellularly and consequently forestall glucose transport. Whether mechanisms be to promote cell-surface translocation of these transporters is not yet known, but information technology has clearly been established that insulin does not raise GLUT6 and GLUT8 cell-surface translocation.

Breakthrough of Na-glucose cotransport [edit]

In August 1960, in Prague, Robert K. Crane bestowed first his discovery of the sodium-glucose cotransport as the mechanics for intestinal glucose preoccupation.[15] Stretch out's discovery of cotransport was the archetypical ever proposal of flux coupling in biological science.[16] Crane in 1961 was the first to articulate the cotransport concept to excuse active carry. Specifically, he projected that the accumulation of glucose in the viscus epithelium across the brush margin membrane was [is] coupled to descending Atomic number 11+ transport cross the brush border. This hypothesis was rapidly tested, refined, and protracted [to] comprehend the active carry of a diverse range of molecules and ions into virtually every cell type.[17]

See also [edit]

  • Cotransport
  • Cotransporter

References [edit]

  1. ^ a b c d e f g h Maier A, Völker B, Boles E, Fuhrmann GF (December 2002). "Characterisation of glucose transport in Saccharomyces cerevisiae with plasma membrane vesicles (countertransport) and intact cells (initial uptake) with unity Hxt1, Hxt2, Hxt3, Hxt4, Hxt6, Hxt7 or Gal2 transporters". FEMS Barm Research. 2 (4): 539–50. Interior Department:10.1111/j.1567-1364.2002.tb00121.x. PMID 12702270.
  2. ^ "List of possible glucose transporters in S. cerevisiae". UniProt.
  3. ^ a b c d e f g h i j k l m n Boles E, Hollenberg CP (Aug 1997). "The molecular genetics of hexose carry in yeasts". FEMS Microbiology Reviews. 21 (1): 85–111. doi:10.1111/j.1574-6976.1997.tb00346.x. PMID 9299703.
  4. ^ a b Diderich JA, Schuurmans JM, Van Gaalen MC, Kruckeberg AL, Caravan Dam K (December 2001). "Functional analysis of the hexose transporter homologue HXT5 in Saccharomyces cerevisiae". Yeast. 18 (16): 1515–24. Interior Department:10.1002/yea.779. PMID 11748728. S2CID 22968336.
  5. ^ Oka Y, Asano T, Shibasaki Y, Lin JL, Tsukuda K, Katagiri H, Akanuma Y, Takaku F (June 1990). "C-terminal short glucose transporter is locked into an inbound-facing form without transport activity". Nature. 345 (6275): 550–3. Interior:10.1038/345550a0. PMID 2348864. S2CID 4264399.
  6. ^ Hebert DN, Carruthers A (Nov 1992). "Glucose transporter oligomeric structure determines transporter use. Reversible oxidation-reduction-dependent interconversions of tetrameric and dimeric GLUT1". The Journal of Biological Chemistry. 267 (33): 23829–38. Interior:10.1016/S0021-9258(18)35912-X. PMID 1429721.
  7. ^ Cloherty EK, Sultzman LA, Zottola RJ, Carruthers A (November 1995). "Net sugar transport is a multistep process. Evidence for cytosolic sugar cover sites in erythrocytes". Biochemistry. 34 (47): 15395–406. Department of the Interior:10.1021/bi00047a002. PMID 7492539.
  8. ^ Hruz PW, Mueckler MM (2001). "Geomorphological analysis of the GLUT1 helpful glucose car transporter (review)". Unit Tissue layer Biology. 18 (3): 183–93. doi:10.1080/09687680110072140. PMID 11681785.
  9. ^ Seatter MJ, De lanthanum Rue SA, Porter LM, Gould GW (February 1998). "QLS motif in transmembrane helix VII of the glucose transporter family interacts with the C-1 position of D-glucose and is involved in substrate selection at the exofacial binding website". Biochemistry. 37 (5): 1322–6. doi:10.1021/bi972322u. PMID 9477959.
  10. ^ Hruz PW, Mueckler MM (December 1999). "Cysteine-scanning mutagenesis of transmembrane segment 7 of the GLUT1 glucose transporter". The Journal of Biological Chemistry. 274 (51): 36176–80. Interior Department:10.1074/jbc.274.51.36176. PMID 10593902.
  11. ^ Thorens B (April 1996). "Glucose transporters in the regulation of intestinal, urinary organ, and liver glucose fluxes". The American Journal of Physiology. 270 (4 Pt 1): G541-53. doi:10.1152/ajpgi.1996.270.4.G541. PMID 8928783.
  12. ^ a b c d e Thorens B, Mueckler M (February 2010). "Glucose transporters in the 21st Century". American Journal of Physiology. Endocrinology and Metabolism. 298 (2): E141-5. doi:10.1152/ajpendo.00712.2009. PMC2822486. PMID 20009031.
  13. ^ Buzzer GI, Kayano T, Buse JB, Burant CF, Takeda J, Lin D, Fukumoto H, Seino S (March 1990). "Molecular biology of mammalian glucose transporters". Diabetes Care. 13 (3): 198–208. doi:10.2337/diacare.13.3.198. PMID 2407475. S2CID 20712863.
  14. ^ Boron WF (2003). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. p. 995. ISBN978-1-4160-2328-9.
  15. ^ Crane RK, Miller D, Bihler I (1961). "The restrictions on possible mechanisms of intestinal transport of sugars". In Kleinzeller A, Kotyk A (eds.). Membrane Raptus and Metabolism. Proceedings of a Symposium held in Prague, August 22–27, 1960. Czech capital: Czech Academy of Sciences. pp. 439–449.
  16. ^ Richard Wright EM, Turk E (February 2004). "The atomic number 11/glucose cotransport family SLC5". Pflügers Archiv. 447 (5): 510–8. doi:10.1007/s00424-003-1063-6. PMID 12748858. S2CID 41985805.
  17. ^ Boyd CA (Border district 2008). "Facts, fantasies and entertaining in animal tissue physiology". Experimental Physiology. 93 (3): 303–14. doi:10.1113/expphysiol.2007.037523. PMID 18192340. S2CID 41086034. The insight from this time that remains in all prevalent text books is the notion of Robert Hart Crane promulgated originally as an vermiform appendix to a symposium theme published in 1960 (Crane et al.. 1960). The Francis Scott Key point here was 'flux yoke', the cotransport of sodium and glucose in the apical membrane of the small intestinal epithelial cellular telephone. Half a centred later this theme has turned into one of the most studied of entirely car transporter proteins (SGLT1), the atomic number 11–glucose cotransporter.

External links [edit]

  • Glucose+Transport+Proteins,+Facilitative at the US National Library of Medicine Medical Subject Headings (MeSH)

why do cells need carrier proteins that transport glucose

Source: https://en.wikipedia.org/wiki/Glucose_transporter

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