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The 'rule' # 1 depends on the number of the aligned chain residues. A graph can be found in Bourne/Weissig Struct. Bioinf. in chapter 25 p 510. I am sure the authors they have this from somewhre earlier, but no ref. br -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, September 21, 2005 3:02 PM To: Yoder, Marilyn Cc: CCP4 Bulletin Board Subject: Re: [ccp4bb]: sequence/structure homology *** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk *** [EMAIL PROTECTED] wrote on 09/21/2005 05:43:57 PM: > My 'googling' skills are failing me and thought perhaps someone here > could point me in the right direction. > > I have two questions. > > 1. It is often stated that with ~30% sequence identity, protein folds > will likely be similar. I can't find a reference to this > 'rule-of-thumb'. I suspect there has been a systematic study showing > this to be the case, but I can't put my finger on it. > > 2. I'm looking for examples where proteins of some size, at least 100 > amino acids, have sequence identity of ~30% but do not have similar > folds. Again, I'm having difficulties finding such and > would appreciate any examples anyone can provide. (Wasn't there a > contest or something where investigators were challenged to introduce > the minimal sequence change that generated a 'different' > structure?). > > Many thanks, > Marilyn Yoder Hi Marilyn - I'm not sure about the answer to #1, but #2 was the "Paracelsus challenge", won by Lynne Regan, Seema Dalal, and Suganthi Balasubramanian in 1997. Check out their paper: Dalal, Balasubramanian, and Regan, NSB 4:548 (1997). They converted a (nearly) all-beta protein into a four-helix bundle by changing only 40% of the amino acids. - Matt -- Matthew Franklin phone:(917)606-4116 Senior Scientist, ImClone Systems fax:(212)645-2054 180 Varick Street, 6th floor New York, NY 10014 Confidentiality Note: This e-mail, and any attachment to it, contains privileged and confidential information intended only for the use of the individual(s) or entity named on the e-mail. If the reader of this e-mail is not the intended recipient, or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that reading it is strictly prohibited. If you have received this e-mail in error, please immediately return it to the sender and delete it from your system. Thank you.
