Protein transport in mitochondria revealed

The TIM23 complex, which regulates the transport of protein to the mitochondria in a cell, is much more complicated than was previously believed. This is shown by Uppsala University researcher Maria Lind in an article in the leading journal Cell.

Together with Agnieszka Chacinska from the University of Freiburg in Germany, Maria Lind from Uppsala University is lead author of the article in Cell.

Agnieszka Chacinska’s and her study shows how the TIM23 complex functions, something that was previously unknown. The TIM23 complex regulates the transport of protein to the mitochondria in the cell. The findings reveal that the TIM23 complex is highly complicated. It can transport proteins even though there is a tension between the two sides of the complex. “The complex opens only a single channel when the protein comes, in order not to disturb the negative or positive charge on the respective sides of the complex,” explains Maria Lind. “It is essential that the voltage created by the difference in the charges be maintained when the mitochondria are to produce energy.”

The TIM23 complex can also change shape depending on where the protein is ultimately to be transported. In this way the same complex can transport proteins to different final destinations. Maria Lind and Agnieszka Chacinska have also identified a new protein, Tim21, which participates in protein transport.

Defects in mitochondria give rise to some one hundred disorders, including Huntington’s disease, Mohr-Tranebjaerg syndrome, Parkinson’s disease, and Alzheimer’s disease. “We need more knowledge about mitochondria if we are to be able to understand these diseases,” avers Maria Lind.

The study was carried out on yeast, which researchers often use as a model organism because it is one of the simplest organisms with mitochondria. “But mitochondria function in the same way in all organisms, and there are many things in yeast cells that are similar to human cells,” says Maria Lind.