Lactose Permease: Difference between revisions

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-====Function of Lactose Permease====
+[[Image:Lacpermmodel.jpg|thumb|left|Physical Model of Lactose Permease based on [[1pv7]] from the [http://cbm.msoe.edu/ MSOE Center for BioMolecular Modeling] ]]
-[[Image:(image info)|left|(Caption)]]  Lactose Permease is a transmembrane  protein that
+===Function of Lactose Permease===
-facilitates the passage of lactose across the phospholipid bi-layer of the cell membrane.  The
+[[Lactose Permease]] or '''galactoside permease''' (PDB entry [[1pv7]]) is a transmembrane protein that facilitates the passage of lactose across the phospholipid bi-layer of the cell membrane.  The transport mechanism used is an active co-transport that uses the inwardly directed H+ electrochemical gradient as its driving force.  As a result, the lactose is accompanied from the periplasm to the cytoplasm of the cell by an H+ proton<ref>PMID:15950162</ref>.  '''Fucose permease''' transports fucose across cell membrane.
-transport mechanism used is an active co-transport that uses the inwardly directed H+
-electrochemical gradient as its driving force.  As a result, the lactose is accompanied from
-the periplasm to the cytoplasm of the cell by an H+ proton.<ref name="A. Green, et.
-al.">[http://www.jbc.org/cgi/content/full/275/30/23240]</ref>
+Lactose is a disaccharide carbohydrate found primarily in mammalian milk.  The disaccharide consists of the monosacharides glucose and galactose.  When the lactose is ingested and absorbed into the cell, the enzyme lactase breaks the disaccharide into its monosaccharide subunits.  These are in turn used in the cellular respiration process and broken down further into energy for the cell.
-Lactose is a disaccharide carbohydrate found primarily in mammalian milk.  It is a
+Lactose permease belongs to the family of so called [[Major Facilitators]].
-disaccharide composed of the monosaccharides glucose and galactose.  When lactose is ingested,
-it is brought into cells in the digestive system by the protein Lactose Permease. Here it is
-broken down into its monosaccharide subunits by the enzyme lactase so it may be used in the
-process of cellular respiration.<ref name="Gita C. Gidwani">[http://www.faqs.org/nutrition/Kwa-Men/Lactose-Intolerance.html]<ref/>
-====Structure of Lactose Permease===={{STRUCTURE_1PV7 |  PDB=1PV7  |  SCENE='Lactose_Permease/Beginning/1'}}
+===Structure of Lactose Permease===
-Lactose permease is a transmembrane protien consisting of N- and C- terminal domains, each with <Scene> six transmembrane helices, symmetrically positioned within the permease.  Six side chains have been determined to be irreplaceable with respect to active transport of
+<applet load="2cfp" size="400" color="white" frame="true" align="right" caption="E. coli lactose permease complex with Hg+2 ions (grey)  [[2cfp]]" />
-lactose.  Those which are crucial for substrate binding are <Scene> Glu126, <Scene> Arg144,
+<scene name='Lactose_Permease/Beginning/1'>Lactose permease</scene> is a transmembrane protein consisting of N- and C- terminal domains (depicted in this model by the blue and red hemispheres), each with six <scene name='Lactose_Permease/Backbone/3'>transmembrane helices</scene> symmetrically positioned within the permease.  There are six sidechains that play an irreplaceable role in the active transport of lactose through the protein.  Three of these sidechains, <scene name='Lactose_Permease/Glu126/3'>Glutamic Acid 126</scene>, <scene name='Lactose_Permease/Arg144/3'>Arginine 144</scene>, and <scene name='Lactose_Permease/Glu269/3'>Glutamic Acid 269</scene> have been shown to be crucial in substrate binding activities.  <scene name='Lactose_Permease/Arg302/2'>Arginine 302</scene>, <scene name='Lactose_Permease/His322/2'>Histidine 322</scene>, and <scene name='Lactose_Permease/Glu325/2'>Glutamic Acid 325</scene> are known to play a significant role in proton translocation(moving the H+ proton) throughout the transport process.  Additionally, there are two residues that are suspected to play an important role in the alignment of the galactopyranosyl end of the substrate.  These are <scene name='Lactose_Permease/Cys148/2'>Cysteine 148</scene> and <scene name='Lactose_Permease/Trp151/2'>Tryptophan 151</scene>.
-and <Scene> Glu269, which may play a role in both substrate binding and proton translocation.
-<Scene>Arg302, <Scene>His322, and <Scene>Glu325 play essential roles in the proton
-translocation series of the co-transport.  Two other important side chains are <scene>Cys148
-and <Scene>Trp151, which are suspected to play an important role in the alignment of the
-galactopyranosyl end of the substrate.
+These sidechains, which make up the active site of the protein, can be found within the large internal <scene name='Lactose_Permease/Cavity/2'>hydrophilic cavity</scene> of the lactose permease.  It is here where the <scene name='Lactose_Permease/Sugar/2'>substrate</scene> is received for transport and it is the location from which it is deposited into the cell.  The currently crystalized form of the permease is considered an 'inward-facing' conformation.  This implies that the hydrophilic cavity mentioned previously is positioned with the opening towards the cytoplasm of the cell.  Conversely, and outward-facing conformation would have the cavity facing the periplasm.
-These sidechains can be found within the large internal <Scene>hydrophilic cavity of the
+{{Clear}}
-protien.  This is the active site where the substrate is recieved for transport.  The
-substrate, traditionally lactose, is shown <scene>here.  Only the <Scene>inward-facing
-conformation, in which the large hydrophilic cavity discussed previously is oriented towards
-the cytoplasm, has been crystallized thus far.
-====References====
+==3D structures of lactose permease==
-<references />
+Updated on {{REVISIONDAY2}}-{{MONTHNAME|{{REVISIONMONTH}}}}-{{REVISIONYEAR}}
-Replace the PDB id after the STRUCTURE_ and after PDB= to load
+{{#tree:id=OrganizedByTopic|openlevels=0|
-and display another structure.
-{{STRUCTURE_1PV7 |  PDB=1PV7  |  SCENE='Lactose_Permease/Beginning/1'}}
+*Lactose permease
+**[[2v8n]] - EcLACY – ''Escherichia coli''<br />
+**[[2cfp]], [[2cfq]], [[1pv6]] - EcLACY (mutant) <br />
+**[[2y5y]] – EcLACY (mutant) + affinity activator<br />
+**[[4oaa]] - EcLACY (mutant) + galactose<br />
+**[[1pv7]], [[4zyr]] - EcLACY (mutant) + galactoside<br />
+**[[5gxb]], [[6c9w]] – EcLACY + nanobody<br />
+**[[6vbg]] – EcLACY (mutant) + nanobody + galactoside derivative<br />
+*Fucose permease
+**[[3o7q]] - EcFUCP<br />
+**[[3o7p]] - EcFUCP (mutant)
+}}
+== References ==
+<references/>
+==Additional Resources==
+For additional information, see: [[Membrane Channels & Pumps]]
+<br />
+==External Links==
+===<font color = 'red'>MSOE Center for BioMolecular Modeling</font>===
+[[Image:Center for BioMolecular Modeling Logo.jpg|left|200px]]
+The physical models shown on this page were designed and built by the MSOE Center for BioMolecular Modeling.    For more information about physical protein modeling, visit the CBM web site at [http://cbm.msoe.edu/ http://cbm.msoe.edu/] .
+[[Category:Topic Page]]