Biological complexity: nucler pores (Introduction)

by David Turell , Saturday, June 06, 2015, 20:28 (3458 days ago) @ David Turell

Large molecules have to go in and out of the nucleus, which has a full surrounding membrane. The pore opens and stretches dynamically. It is not rigid:-http://phys.org/news/2015-06-reveals-key-interaction-channel-cell.html-"But ongoing work in Blobel's lab indicates the central channel is anything but rigid. In previous research, a team from his lab identified a flexible ring in the middle of the central channel, the diameter of which was determined by two of the nuclear pore complex's approximately 30 nucleoporins, Nup58 and Nup54, which associate and disassociate from one another in what the researchers dubbed the ring cycle. When these two nucleoporins associate, the ring dilates to a diameter of up to 50 nanometers, a size capable of accommodating a ribosomal subunit, the largest and most complex of the cell's molecular freight. Then, when the nucleoporins separate, the single ring divides into three rings with diameters of 20 nanometers.-" This most recent research, conducted by postdoc Junseock Koh in Blobel's laboratory, examines how a transport factor known as karyopherin initiates the dilation of the ring. To accomplish this, Koh measured changes in heat during reactions between the three components, karyopherin, Nup58, and Nup54. Biophysical data like this reveals the energy dynamics during these reactions, and so provides clues to the behavior of the molecules involved. To tease apart this complex system, Koh mathematically analyzed the data collected at various conditions. His results revealed an unexpected role for a disordered region of Nup58.-"'We found that when one karyopherin molecule binds to at least two disordered regions of Nup58, it stabilizes Nup58 in such a way that the dilated conformation—in which the neighboring ordered region of Nup58 links up with Nup54—becomes more favorable. As a result, the more karyopherin molecules are present, the more the ring dilates," Koh says. "Based on these results, we were able to develop a framework for predicting the extent to which a ring will dilate given the amount of transport factors present.'"-
And just how does the Darwin theory explain this? It can't.