Biological complexity: amazing cell pore complexity (Introduction)

by David Turell , Friday, December 02, 2016, 00:40 (2914 days ago) @ David Turell

Here are two articles about the highly complex nuclear membrane pores. Since the nucleus carries the codes for cellular function the entrance and exit through the membrane pores is highly protected for accuracy. The first article is a summary of the number of proteins involved in just one cell nucleus:

http://www.the-scientist.com/?articles.view/articleNo/47478/title/Doors-and-Pores/&...

"The awesome architecture of the gateways to the nucleus:

"Nuclear pore complexes raise jigsawing to a far more rarified level. In their feature, Daniel Lin and André Hoelz describe these “massive molecular machines” as put together from “more than 1,000 protein subunits with a total molecular mass of approximately 120 million daltons—the equivalent of more than 6.5 million water molecules.” The subunits self-assemble to form more than 30 types of nucleoporin proteins, 17 of which constitute the beautifully symmetric three-ringed core of the nuclear pore complex. Through the pore’s central channel smaller molecules enter and exit by diffusion while proteins or ribosomal units in their native states hop a ride on cargo ships known as karyopherins."

The second article shows the diagrams and there is a link to a very long descriptive article for further review:

http://www.the-scientist.com/?articles.view/articleNo/47560/title/Infographic--The-Nucl...

Descriptions of diagrams: Be sure to look at them

"Macromolecules—including proteins, tRNAs, and even fully assembled pre-ribosomal subunits—are transported through the NPC in their native states with the help of proteins called karyopherins that bind to both target molecules and to FG repeats. Upon entering the nucleus, incoming karyopherins release their cargo when they are bound by RanGTP, the GTP-bound conformation of a small GTPase protein called Ran. For cargoes leaving the nucleus, RanGTP is often incorporated into karyopherin transport complexes inside the nucleus, but encounters the Ran-activating protein RanGAP after exiting. RanGAP triggers Ran to hydrolyze GTP into GDP, causing a conformational change and the release of the cargo into the cytoplasm.

"Messenger RNAs (mRNAs) transcribed in the nucleus are loaded with diverse proteins to form messenger ribonucleoproteins (mRNPs) that are exported through the NPC. These proteins include Nxf1 and Nxt1, which bind to FG repeats in the central channel. Nucleoporins on the cytoplasmic side of the pore recruit and activate an ATPase to remove Nxf1/Nxt1, freeing the mRNA to be translated by the ribosome."

Comment: Any reasonable person will see that these pores are extraordinarily complex in structure and function. They obviously require exquisite planning that only a great mind can accomplish. And the complete architecture is not fully elucidated at this time. How much complexity is required to make this point obvious? Not by chance!

This is the link to the very long article:

http://www.the-scientist.com/?articles.view/articleNo/47529/title/Nuclear-Pores-Come-in...