Lactose Permease

This page refers to a physical model based on 1pv7 from the MSOE Center for BioMolecular Modeling

Physical Model of Lactose Permease

Function of Lactose PermeaseFunction of Lactose Permease

Lactose Permease 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.

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 permease belongs to the family of so called Major Facilitators.

Structure of Lactose PermeaseStructure of Lactose Permease

spinqualitylabelsall models Lactose Permease based on 1PV7 Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

is a transmembrane protein consisting of N- and C- terminal domains (depicted in this model by the blue and red hemispheres), each with six 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, , , and have been shown to be crucial in substrate binding activities. , , and 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 and .

These sidechains, which make up the active site of the protein, can be found within the large internal of the lactose permease. It is here where the is recieved 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.

MSOE Center for BioMolecular ModelingMSOE Center for BioMolecular Modeling

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/ .