{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

L11 - We are on chapter 16 the cytoskeleton Today we will...

Info icon This preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
We are on chapter 16: the cytoskeleton Today we will finish microtubules: binding proteins and function and then move onto actin Exam next week 11/10/09 Class survey for the break
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Signaling networks are complicated….but I expect you to know the basic 4 and only 4 GPCR and RTK pathways
Image of page 2
HOW ARE THESE TUBULIN HETERODIMERS USED TO MAKE A MICROTUBULE? 1. Head to tail interactions form a protofilament. 2. Lateral interactions between protofilaments form a hollow tube - a microtubule There are 13 protofilaments/microtubule 25nM across - hollow inside is 14 nM across. No known function for hollow inside. MICROTUBULE STRUCTURE Microtubules are polymers of tubulin. There are two tubulin proteins - alpha and beta. Basic unit of the microtubule is the tubulin heterodimer - contains one alpha and one beta tubulin. Alpha and beta tubulin are highly related - 450 amino acids long Very abundant and highly conserved proteins.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
DYNAMIC INSTABILITY In situations where microtubules are nucleated at one end, assembly and disassembly of heterodimers occurs only at the + end Current model for this is the dynamic instability model 1- Minus end of microtubules lies in the MTOC - microtubule organizing center (see later) 2-growth occurs only at the plus end 3-loss occurs only from the plus end 4- two growth states - slow growth or rapid depolymerization 5-microtubule is stable only if the plus end reaches a cap
Image of page 4
TREADMILLING and under this circumstance elongation is still faster than hydrolysis at the + end (because adding a T form subunit is faster), but elongation becomes slower than hydrolysis at the – end so the terminal units go to the D form. As the filament grows, the subunit concentration falls. Usually in a cell, [GTP] > [GDP] so most free subunits are in the T form (GTP-form) and the filament grows from both ends. But the cell is dynamic and the rate of subunit addition changes with fluctuating subunit concentration.
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Treadmilling occurs at intermediate subunit concentrations, higher that Cc of the T form (the filament still adds subunits to the + end), but lower than the Cc of the D form (the filament simultaneously loses subunits from the – end) Critical concentration is the concentration at which the rate of subunit addition equals to that of subunit loss TREADMILLING
Image of page 6
MICROTUBULE STRUCTURE, ASSEMBY and DISASSEMBY
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The number and location of cytoskeletal filaments are tightly controlled within the cell •Tubulin subunits are present in the cell at concentrations above the critical concentration. •Yet most tubulin is not assembled into polymer. •How do cells ensure that microtubules and actin filaments form at the correct time and place?
Image of page 8
MAPS: Microtubule Associated Proteins
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Cells use multiple mechanisms to regulate microtubule assembly, disassembly and organization in the cell: 1) Nucleating sites determine where polymers form.
Image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern