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Subject: RE: Neighboring Phosphorylation Sites
Date: Tue, 12 Jun 2001 17:03:40 -0500
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I looked up some sequences that I had laying around for Alpha Casein and
beta casein when I was trying them out on the IMAC columns. The masses for
the multiple phosphorylated tryptic fragments were right on BUT I didn't run
MS/MS to see if they were in the correct position. Both can be obtained
through Sigma fairly cheaply, then digested. Fragments, if I remember
correctly were fairly easy to HPLC purify which would be a good method to
obtain them in quanity to check it out. The masses were very homogeneous
suggesting 100% phosphorylation. Too bad all of the phosphorylations we
chase around aren't 100% phosphorylated. They would be a lot easier to
find!
A-Casein
DIGpSEpSTEDQAMEDIK 2 phos ser- Supposed to be the 2 Sers not the Thr
QMEAEpSIpSpSpSEEIVPNpSVEQK - 5 x phos ser
B-casein
RELEELNVPGEIVEpSLpSpSpSEESITR - 4 x phos ser - Again, the mass checked out
but I didn't MS sequence to show that the last Serine or Threonine in the
peptide weren't phosphorylated instead.
Gary Lange
gary.w.lange@pharmacia.com
Pharmacia
700 Chesterfield Parkway North
Mail Zone AA2I
St. Louis, MO 63198
636-737-6602
fx 636-737-7005
-----Original Message-----
From: Michael Curtis [mailto:curtism@mail.upstate.edu]
Sent: Monday, June 11, 2001 3:24 PM
To: Recipients of ABRF List
Subject: Neighboring Phosphorylation Sites
Hello.
I am currently working on a phosphorylation project and have a question
concerning neighboring phosphorylation sites. Does anyone know of an
example of
two phosphorylateable residues being directly next to each other and both
being
phosphorylated? Or sites that are very close?
For example:
Directly next to each other:
i.e XXSTXX giving XXSpTpXX upon phosphorylation
Or very close by:
i.e. XXS(X1-2)TXX giving XXSp(X1-2)TpXX upon phosphorylation
I am wondering if phosphorylation of one would sterically hinder the
phosphorylation of the other. Any instance of these cases that you know
about or
any insight you have on this issue would be greatly appreciated.
Thanks in advance.
Mike
Mike Curtis
UMU
curtism@mail.upstate.edu
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