Stories
Slash Boxes
Comments

SoylentNews is people

posted by janrinok on Saturday August 08 2015, @10:17PM   Printer-friendly
from the say-cheese dept.

Microtubules, hollow fibers of tubulin protein only a few nanometers in diameter, form the cytoskeletons of living cells and play a crucial role in cell division (mitosis) through their ability to undergo rapid growth and shrinkage, a property called "dynamic instability." Through a combination of high-resolution cryo-electron microscopy (cryo-EM) and a unique methodology for image analysis, a team of researchers with Berkeley Lab and the University of California (UC) Berkeley has produced an atomic view of microtubules that enabled them to identify the crucial role played by a family of end-binding (EB) proteins in regulating microtubule dynamic instability.

During mitosis, microtubules disassemble and reform into spindles that are used by the dividing cell to move chromosomes. For chromosome migration to occur, the microtubules attached to them must disassemble, carrying the chromosomes in the process. The dynamic instability that makes it possible for microtubules to transition from a rigid polymerized or "assembled" nucleotide state to a flexible depolymerized or "disassembled" nucleotide state is driven by guanosine triphosphate (GTP) hydrolysis in the microtubule lattice.

"Our study shows how EB proteins can either facilitate microtubule assembly by binding to sub-units of the microtubule, essentially holding them together, or else cause a microtubule to disassemble by promoting GTP hydrolysis that destabilizes the microtubule lattice," says Eva Nogales, a biophysicist with Berkeley Lab's Life Sciences Division who led this research.

Nogales, who is also a professor of biophysics and structural biology at UC Berkeley and investigator with the Howard Hughes Medical Institute, is a leading authority on the structure and dynamics of microtubules. In this latest study, she and her group used cryo-EM, in which protein samples are flash-frozen at liquid nitrogen temperatures to preserve their natural structure, to determine microtubule structures in different nucleotide states with and without EB3. With cryo-EM and their image analysis methodology, they achieved a resolution of 3.5 Angstroms, a record for microtubules. For perspective, the diameter of a hydrogen atom is about 1.0 Angstroms.


Original Submission

 
This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 1, Informative) by Anonymous Coward on Sunday August 09 2015, @12:31AM

    by Anonymous Coward on Sunday August 09 2015, @12:31AM (#220063)

    Microtubules bind GTP and can assemble with each other to form polymers. Their assembly is regulated by the hydrolysis of the nucleotide GTP, which results in a change in the protein's shape, that affects its strength of association with other microtubules.

    Starting Score:    0  points
    Moderation   +1  
       Informative=1, Total=1
    Extra 'Informative' Modifier   0  

    Total Score:   1  
  • (Score: 0) by Anonymous Coward on Sunday August 09 2015, @12:43AM

    by Anonymous Coward on Sunday August 09 2015, @12:43AM (#220066)

    So GTP polymers are involved? First time Ive heard that idea, source?

    • (Score: 2, Informative) by Anonymous Coward on Sunday August 09 2015, @12:58AM

      by Anonymous Coward on Sunday August 09 2015, @12:58AM (#220072)

      The protein binds a single GTP.
      The hydrolysis of the GTP removes a phosphate and produces GDP. The protein bound to GDP assumes a different shape than when the guanosineĀ had three phosphates. The change in shape destabilises the lattice of microtubules and can result in their disassembly.

      • (Score: 0) by Anonymous Coward on Sunday August 09 2015, @01:11AM

        by Anonymous Coward on Sunday August 09 2015, @01:11AM (#220077)

        Ok, what you describe matches with my understanding. So "depolymerized nucleotide state" is just poor wording. I guess polymerized could also refer to the phosphates but I've never heard the term used that way.

        • (Score: 1, Informative) by Anonymous Coward on Sunday August 09 2015, @03:15AM

          by Anonymous Coward on Sunday August 09 2015, @03:15AM (#220126)

          It is poor wording.
          The nucleotide state of the protein in this case is either GTP or GDP-bound. The GTP-bound microtubule state is one that promotes polymerization with other microtubules while the GDP-bound microtuble state is one that destabilizes association with other microtubles. The latter is what they refer to as "depolymerized nucleotide state".

          • (Score: 0) by Anonymous Coward on Sunday August 09 2015, @06:01AM

            by Anonymous Coward on Sunday August 09 2015, @06:01AM (#220150)

            Yep, it makes sense that's what they were getting at. Thanks.

            • (Score: 2) by janrinok on Sunday August 09 2015, @01:04PM

              by janrinok (52) Subscriber Badge on Sunday August 09 2015, @01:04PM (#220235) Journal
              This sort of discussion is why I come to SN! You've made at least one editor happy, thank you.