Scientists who developed a technology for identifying and targeting unique protein receptor ZIP Codes on the cellular surface have found a way to penetrate the outer membrane and deliver engineered particles — called iPhage — to organelles inside the cell.
In a paper recently published online in Nature Communications, the team led by researchers at The University of Texas MD Anderson Cancer Center reports packaging the phage particles with a peptide called penetratin to reach inside the cell.
Most newly produced proteins in a cell need to be transported to the proper place before they can be put to work. For proteins to find their way, they have a built-in signal linked to them, a kind of address label. Moreover, they are helped by a particle that guides them to the cell membrane. In a new study published in the journal Nature Structural and Molecular Biology, researchers at Umeå University in Sweden show how this interaction works.
Scientists have visualized the structure of a transporter protein (Microbacterium hydantoin permease, or Mhp1) and have shown how the protein opens and closes to allow hydantoin molecules across the membrane and into the cell. The work has significance because of hundreds of similar transporters found in the membranes of human cells.
Professor So Iwata from Imperial College London’s Division of Molecular Biosciences in the department of Life Sciences remarked: “Transporter proteins play an important role in the human body – they are responsible for letting different substances, including salts, sugars and amino acids, into our cells and are targets for a large number of drugs. Understanding the details of how this transport mechanism works may help researchers design new, more effective drugs in the future.”
The collaborative work began in 2000 with the Ajinomoto Company from Japan which first recognized Mhp1 in Microbacterium liquefaciensand its role in the uptake of hydantoin. Workers at the University of Leeds amplified the expression of the protein in Escherichia coli. Professor Iwata and co-workers at the Membrane Protein Laboratory, an outstation of Imperial College built the picture of Mhp1 protein binding to hydantoin.
Researchers observed that Mhp1 opens up on its outer side to allow the hydantoin molecule to move into the membrane. Once bound, the opening to the outside of the membrane is closed after which the inward-facing side of the membrane opens to release hydantoin into the cell.
Abstracted from Scienceexpress, October 16, 2008 and ScienceDaily, October 17, 2008.