Scientists at Rice University have published new information about how motor proteins interact. Their study shows that when motor proteins travel together, they tend to move at a slow and steady pace for optimal transport. In the past these interactions were not considered significant however theoretical biophysicist Anatoly Kolomeisky, the lead author of the study, says that cell dynamics are affected by even small changes, such as medication and the way proteins interact is worthy of study. His group's paper in the Journal of Physics A: Mathematical and Theoretical describes a new theoretical approach to study the effect of intermolecular interactions on the dynamics of motor proteins
The team built a new mathematical model that analyzes motor protein activity and demonstrates that both strong and weak interactions are important to regulate the flux, or movement, of motor proteins.
"It's known that these motor proteins work together, and that when two motors are next to each other, they interact," Kolomeisky said. "It's relatively weak, but it is an interaction. The question we raised is, ‘What is the role of these interactions in overall cooperation?' What we've done that other groups have not is treat these interactions in a thermodynamically consistent way," he said. "
Using a model known as totally asymmetric simple exclusion process, they created a simulation of protein transport where they could vary the amount of interaction between motors. Kolomeisky said. "Surprisingly, we found in our simulations that having no interaction between the motors is not optimal." When the team manipulated the simulation in different ways to account for the thermal dynamics of attraction and repulsion they found that the motors could adjust for fluctuations in their environment. Gathering together would slow down movement, while separating and keeping more space between motors would speed up the transport along the simulated microtubules.
Over time both strong attractions and repulsions became diminished, as if wearing out. This lessening of the dynamic impacted particle flow leading researchers to surmise that a "just right" amount of interaction; an intermediate amount of attraction or repulsion was better than an extreme amount. Surprisingly their model showed that weaker repulsions lead to maximum movement. It seems that motor proteins are somewhat hobbled by strong attractions. When there was a large amount of attraction between proteins, clusters formed and would often stop the motors completely because individual particles became trapped.
The team built simulations of various sizes to insure their data was as close to reality as possible. "We realized that first, biological systems might not be optimized for maximal flux but for something else. Second, our theory shows the system is very sensitive to small changes. In other words, a motor can easily adjust itself. You change a little bit of the interaction, and the motors change flux significantly." Kolomeisky said the new work helps chip away at the mysteries that remain to be solved in cellular dynamics. "The more we understand about fundamental features of these biological phenomena, the better for us," he said. "This is one small part of a huge puzzle."
