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okadaic acid

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okadaic acid

Postby KTK » Sat Apr 23, 2005 10:21 pm

Are the protein kinases and phosphatases that control Wee1 and Cdc25 specific for serine/theronine side chains or tyrosine side chains? How do you know?
Last edited by KTK on Thu May 12, 2005 11:07 am, edited 2 times in total.
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Postby Chris4 » Mon Apr 25, 2005 1:09 pm

:evil: :( Im so annoyed. I was researching the answer to your question and tried to open a PDF about the cell cycle and wee1 and firefox crashed. And i lost everything i'd typed for the reply. I love firefox but it doesnt like large PDFs. :evil:
From what i'd found CDC25 can be phosphorylated on several serine residues. 5 if i remember correctly. It has been shown that CDC25C is highly phosphorylated at the G2-to-M transition and has five serine/threonine-proline sites: Thr48, Thr67, Ser122, Thr130, and Ser214. From here:http://ajpcell.physiology.org/cgi/content/full/284/2/C349#B32
also From here: http://www.sciencemag.org/cgi/content/a ... f_ipsecsha
results indicate that serine-216 phosphorylation and 14-3-3 binding negatively regulate Cdc25C and identify Cdc25C as a potential target of checkpoint control in human cells.

I'll have a look at the rest of the questions later, (i need to get back to work),
OK. FOUND SOMETHING :lol: .WHENS YOUR HOMEWORK DUE IN?
http://www.msu.edu/course/mmg/409/hw11.pdf
Its amazing what google finds.
This is incredible. You have the answers on the web: http://www.msu.edu/course/mmg/409/hw11a.pdf
http://darwin.nmsu.edu/~molbio/mcb520/answers6.html
Ok. the questions are slightly different. Your first question is identical to the previous ones.
2) Okadaic acid question - This helps " Okadaic acid has no effect on Cdc2 phosphorylation because it is phosphorylated on a tyrosine residue. Tyrosine phosphatases are unaffected by okadaic acid. The decrease in Cdc2 phosphorylation is a consequence of the change in activation of Wee1 kinase and Cdc25 phosphatase." And this "Why does Okadaic acid cause an increase in Phosphorylation of Wee 1 and Cdc25 and
a decrease in P of Cdc 2?
Phosphate on Cdc 2 is on tyrosine. Because odadaic acid causesCdc25 to be
active, this causes a removal of the inhibitory tyrosine phosphate and Cdc2 runs faster on
the gel." CDC2 is cdk1. (yeast/mammalian).

3) Final question: Bit tricky: MPF activates cdc25 and inhibits wee1. active cdk would phosphorylate cdc25 and wee1. WAIT. Is this your homework:http://www.msu.edu/course/mmg/409/hw11.pdf
the last question says "Can you explain how the appearance of a small amount of active MPF" NOT ACTIVE CDK! Active MPF would make a lot more sense. Im really confused now. You'll have to get back to me on all that. :?
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Postby Chris4 » Mon Apr 25, 2005 1:20 pm

Note for question 2) Okadaic acid is an inhibitor of serine/threonine protein phosphatases. it is specific for serine/threonine phosphatases. Thats why it causes an increase in phosphorylation of wee1 and cdc25 as its specific for these serine/threonine phosphatases. DO YOU NEED EXPLAIN WHY ITS SPECIFIC? That could involve some tricky biochemistry.
The decrease in phosphorylation of cdk is quote "The decrease in Cdc2 phosphorylation is a consequence of the change in activation of Wee1 kinase and Cdc25 phosphatase."
Hope thats a bit clearier. ?
Your going to have to put all this in your own words as your teacher will know the past answers are on the web.
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Cdc25, Wee1, and okadaic acid

Postby KTK » Tue Apr 26, 2005 1:17 am

Hi, Chris4,

Thank you sooo much for helping me out. I will take a look at the stuff that u have posted. Again, I really appreciate it.

Sincerely,
KTK
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