Tug of war in the cell

The process of transporting in our body's cells is like the process of transporting goods on the roads. Molecular engines, which are special protein molecules, act as cargo trucks. They carry cell packs on their backs and follow microscopic tubes - the cell's transport pathway. However, these molecular ' drivers ' are a billion times smaller than trucks, and they can only move the most from one end of the micro-tube to the other, depending on the type. what cell

Scientists at the Max Planck Institute of Colloids and Interfaces in Potsdam (Germany) have just discovered an interesting thing about this transport process through computer simulations. The molecular engine struggled on a crowded route like a busy area of ​​pedestrians rather than on highways. They also have to compete with molecules that want to move in the opposite direction.

Some molecules must always participate reluctantly in a tug-of-war, such as kinesin molecules and dynein-type molecules. The kinesin motors move toward the end of the microscopic tube that biologists call an anodes, while the dynein motors move back to the cathode. The discovery by Max Planck scientists has shown that the more powerful engine group will determine the direction of transportation. In this war, the opposite engines will leave the microscopic tube. It was previously thought that there was a sorting system that allowed only one group of engines to operate, and there was a rotation between one group and the other.

Melanie Mueller - one of the scientists involved in the project - said: 'This duo is the simplest mechanism we can imagine. But consider the characteristics of each individual engine determined by experiment. They create a strong, non-linear response when pulled. ' A motor of the ventricular group is subject to strong force and will be pushed out of the microscopic tube quickly.

The struggle of two groups of molecular-level engines: The green ' item ' is transported by two groups of molecular engines along a yellow micrograph. The red engine team pulls the item to the right in the positive pole, and the green team pulls to the left with the negative pole. When both teams pull, they cancel each other's force so the item hardly moves. As soon as a team prevails, it will move very fast and the other engine group will be separated from the microtubule. (Photo: Melanie Mueller, MPI of Colloids and Interfaces)

The remaining engines of this group must then receive the power of the dominant team so they are also pushed out even at a faster rate than before. Under the act of dominance, the weaker engines are forced to give up and will be pushed out of the micro-tube gradually until there is no longer any engine left. So the winning team can transport the goods quickly without obstruction.'However, the cell will not neglect the chance that it will ensure the item is delivered to the right place. The executive proteins will have to intervene if needed , 'Melanie Mueller said.

Scientists have studied the transport of fat molecules in fruit fly embryos to find out if this model can be applied in practice. Experimental observation of the transport mechanism conducted earlier explained that. The item is transferred on the micro-tube without moving directly from one end to the other end of the tube. It is always pulled in the opposite direction. However, weaker engines also occasionally push dominant engines out of the microtubule because sometimes the heat has blown away these dominant engines. Therefore, commodity molecules are transported in both directions.

Melanie Mueller explains: Two-way transportation is very flexible. It can change direction if the item passes the destination or changes the shipping speed. In this enticing mechanism, the dominant group will pull the opposite motor group as well as the goods in the cell. That mechanism also solves a logistical problem in cells. Helps bring the motors to the end of the microcapsules where they can move, helping to limit the stasis of the same type of motor at the destination.

Melanie Mueller said: ' Although the mechanism is very simple, the process of one molecule transported by two groups of engines shows a very complicated activity '. There are 7 different types of movements. It is a combination of the positive and negative polarities of the microscopic tube plus the pause that all can target the transported molecule. The probability of moving in a particular direction or pause as well as the time spent on navigation depends on the characteristics and number of engines involved. Cells use them to run the transport process. If a group of engines pulls stronger or faster, the transporter will move to the cathode instead of the positive or may stop.

According to Melanie Mueller, 'simple but effective cellular contraction mechanism can be applied in chips' . Simulation of biological processes, engine groups can transport certain molecules to specific reaction sites on the chip and bring back reactive products. 'Our quantitative theory provides an optimistic view of the application of transport engine characteristics for this purpose'.

Reference: Two-way interactive mechanism of molecular motors in cargo transport - Melanie JI Mueller, Stefan Klumpp and Reinhard Lipowsky, PNAS Early Edition, March 17, 2008.