Protein Science
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Protein Science (2007), 16:1439-1448. Published by Cold Spring Harbor Laboratory Press. Copyright © 2007 The Protein Society
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplemental Research Data
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Saxl, R. L.
Right arrow Articles by Maley, F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Saxl, R. L.
Right arrow Articles by Maley, F.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

Significance of mutations on the structural perturbation of thymidylate synthase: Implications for their involvement in subunit exchange

Ruth L. Saxl1,, Gladys F. Maley, Charles R. Hauer, Robert Maccoll, Liming Changchien, and Frank Maley

The Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA

(RECEIVED August 22, 2006; FINAL REVISION March 27, 2007; ACCEPTED March 27, 2007)

Wild-type thymidylate synthase (WT-TS) from Escherichia coli and several of its mutants showed varying degrees of susceptibility to trypsin. While WT-TS was resistant to trypsin as were the mutants C146S, K48E, and R126K, others such as Y94A, Y94F, C146W, and R126E were digested but at different rates from one another. The peptides released from the mutants were identified by mass spectrometry and Edman sequence analysis. The known crystal structures for WT-TS, Y94F, and R126E, surprisingly, showed no structural differences that could explain the difference in their susceptibility to trypsin. One explanation is that the mutations could perturb the dynamic equilibrium of the dimeric state of the mutants as to increase their dissociation to monomers, which being less structured than the dimer, would be hydrolyzed more readily by trypsin. Earlier studies appear to support this proposal since conditions that promote subunit dissociation in solutions of R126E with other inactive mutants, such as dilution, low concentrations of urea, and elevated pH, greatly enhance the rate of restoration of TS activity. Analytic ultracentrifuge studies with various TSs in urea, or at pH 9.0, or that have been highly diluted are, for the most part, in agreement with this thesis, since these conditions are associated with an increase in dissociation to monomers, particularly with the mutant TSs. However, these studies do not rule out the possibility that conformation differences among the various TS dimers are responsible for the differences in susceptibility to trypsin, particularly at high concentrations of protein where the WT-TS and mutants are mainly dimers.

Keywords: mutations; thymidylate synthase; subunit dissociation; proteolysis; mass spectrometry; peptide identification


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2007 by The Protein Society.