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Research -G.Ames Lab -Introduction -Symposium Presentation -My Work
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Index -Introduction -Histidine Permease -Transport Cycle -HisJ Structure -HisQ and HisM Topology |
1 - A single cycle of transport through the histidine permease requires the interaction of the closed, liganded form of HisJ with the HisQMP2 complex. Once HisJ binds its substrate, L-histidine in this case, it shuttles its cargo to the HisQMP2 complex.
2 - The interaction of HisJ with the HisQMP2 complex induces a conformational change within the complex. It is believed that the signal is primarily transduced from HisJ to the HisQ subunit. There is some evidence that HisM also plays a role in the signal transduction, but its role is minor at best. The induced conformational change within the complex stimulates the two HisP subunits to hydrolyze the bound ATP. This reaction provides the energy necessary to translocate the substrate across the inner membrane.
3 - Once ATP hydrolysis occurs, the substrate is translocated from the periplasm into the cytosol of the bacteria.
4 - In order for the next cycle of transport to occur, ADP dissociates from the HisP subunits while HisJ dissociates from the transmembrane subunits.
5 - ATP
is loaded onto the HisP subunits and the complex is ready for the next
cycle of transport.