How does the open protein 'door' come into the cell?

The protein-used measure allows cells to absorb chemicals from their surroundings, while keeping other substances outside, first revealed in detail on October 16, Science magazine. Express.

The scientists who conducted the study built the structure of a protein called Microbacterium hydantoin permease, or 'Mhp1', that exists in the cell membrane of bacteria. It belongs to the 'transporting' protein group , which helps cells absorb some substances from their surroundings. This is the first time scientists have described the opening and closing mechanisms of transport proteins that allow molecules to travel through the membrane to enter the cell.

Professor So Iwata of the Molecular Biology Unit, Faculty of Life Sciences, Imperial London College, one of the authors of the study, explained that it is important to understand the structure of the Mhp1 transport protein in bacteria. Because hundreds of similar transport proteins can be found in human cell membranes.

"Transport proteins are important in the human body - they are responsible for allowing different substances, including salt, sugar and amino acids, to enter our cells," he said. In addition, these proteins are the target for many drugs. Understanding the details of how these transport proteins work can help researchers make new drugs more effectively in the future. '

Research on the protein mentioned above started in 2000, with a joint project with Japan's Ajinomoto Company. This company works with a bacterium called Microbacterium liquefaciens that has Mhp1 protein in cell membranes.The results show that Mhp1 helps absorb amino acid-like molecules called hydantoins through the cell membrane.

Professor Peter Henderson of Leeds University, co-author of the study, said: 'The main problem is making enough proteins for structural research. We have developed methods to stimulate the expression of Mhp1 protein in the host, Escherichia coli, along with protein refining processes from cell membranes. Since then we have a 'pipeline' that provides a significant amount of cell membranes containing Mhp1 protein for colleagues at Imperial '.

The Mhp1 transport protein in the bacteria takes the hydantoin molecule through the cell membrane.(Photo: Imperial University London)

Professor Iwata and colleagues analyzed the structure of Mhp1 using the device at the Membrane Protein Laboratory (MPL), an Imperial College research station at the Diamond Light Source, Oxfordshire National Recycling Facility. The household used MPL, which is a center dedicated to the study of cell membrane protein structures, in order to accurately model the Mhp1 protein associated with hydantoin.

The researchers analyzed the structure of Mhp1 before and after it introduced the hydantoin molecule into the cell. They also used the structure of another transport protein, vSGLT, to understand the post-molecular absorption phase.These three structures reveal in detail how Mhp1 transports hydatoin molecules through cell membranes.

The Mhp1 protein opens outside, allowing the hydatoin molecule to move inside. When hydatoin is absorbed, the 'door' to the outside world is closed, making sure no other substances enter. Then the inner face of the protein opens up the hydantoin into the cell.

Professor Iwata commented on the meaning of the findings: 'Our research has revealed the molecular function of membrane proteins in a very detailed way. We now understand how proteins allow hydatoin to move through the cell membrane without absorbing any other substance. The mechanism is also used by many membrane proteins, including proteins in the human body. Therefore, this is an important step in understanding the basics of the processes that appear in our cells. '

Professor Iwata leads a group of international scientists at the Membrane Laboratory at Diamond Light Source. MPL is the result of co-operation with Imperial London and Diamond Light Source Colleges, funded by the Wellcome Trust and the Japan Science and Technology Agency.

Professor Henderson is the scientific director of the European Union's European Membrane Protein Center, which promotes collaborative research on membrane proteins between 18 European countries.

The Science Express study was carried out by researchers from Imperial College and University of Leeds, in collaboration with scientists from Japan and Iran. The study was funded by BBSRC, the Japan Science and Technology Agency, the European Union, the Wellcome Trust and Ajinomoto Company.