To reveal the mechanism of insertion of β - barrel protein into mitochondrial membrane

In a new study, researchers from the University of Freiburg in Germany have successfully described how the so-called beta barrel protein is inserted into the mitochondrial membrane These proteins allow mitochondria to import and export molecules Based on this finding, the research team led by Professor Nils Wiedemann and Professor Nikolaus Pfanner worked with the research team led by Professor Carola hunter, Ph.D., to clarify a basic problem in protein biochemistry The relevant research results were published in the Science Journal on January 19, 2018, and the paper title is "membrane protein insertion through a mitohondrial β - barrel gate"   Mitochondria, which provide energy for cells, contain about 1000 protein molecules transported from the cytosol For this reason, their outer membrane has a protein input channel composed of molecules with barrel structure (so-called β - barrel protein) In mitochondria, energy from nutrients is used to produce the cellular energy molecule adenosine triphosphate (ATP) ATP is transported to the cytosol through the barrel pore on the outer membrane of mitochondria, which provides fuel for human cells About 30 years ago, a team led by Professor Georg Schulz of the University of Freiburg reported the structure of β - tubulin: protein chains extending in the opposite direction form lamellae, which form a hollow cylinder structure by connecting the first chain of protein and the last chain of protein Since then, scientists have wanted to know how such channel forming protein molecules are inserted into biological membranes Subsequently, the sorting and assembly machinery (SAM) was identified in the outer mitochondrial membrane, which is necessary for the insertion of β - barrel protein into the mitochondrial membrane Sam50 is the name of the central subunit of Sam, which is used to form beta bucket protein This is the starting point of the current study Through experiments, Dr Alexandra h ö HR confirmed that the last chain of the newly synthesized β - barrel protein was introduced between the first chain and the last chain of the β - barrel structure of sam50, and the β - barrel structure of sam50 was also the starting position of this β - barrel protein inserted into the mitochondrial membrane Together with Caroline Lindau, she confirmed that the newly synthesized β - barrel protein was loaded into the side opening of sam50 one by one until the complete β - barrel protein was released into the mitochondrial membrane In view of the fact that both mitochondria and chloroplasts with photosynthetic capacity originate from the same bacterial ancestors, this new study not only helps to better understand the formation and function of mitochondria, but also provides new insights for the formation of chloroplasts and bacteria.