HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gustafson, C. L.T. Articles by Van Etten, R. L. Search for Related Content PubMed PubMed Citation Articles by Gustafson, C. L.T. Articles by Van Etten, R. L. Social Bookmarking                   What's this?

Solution structure of the low-molecular-weight protein tyrosine phosphatase from Tritrichomonas foetus reveals a flexible phosphate binding loop

¹ Department of Chemistry and ² Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2084, USA

(RECEIVED June 3, 2005; FINAL REVISION July 15, 2005; ACCEPTED July 15, 2005)

Eukaryotic low-molecular-weight protein tyrosine phosphatases (LMW PTPs) contain a conserved serine, a histidine with an elevated pK_a, and an active site asparagine that together form a highly conserved hydrogen bonding network. This network stabilizes the active site phosphate binding loop for optimal substrate binding and catalysis. In the phosphatase from the bovine parasite Tritrichomonas foetus (TPTP), both the conserved serine (S37) and asparagine (N14) are present, but the conserved histidine has been replaced by a glutamine residue (Q67). Site-directed mutagenesis, kinetic, and spectroscopic experiments suggest that Q67 is located near the active site and is important for optimal catalytic activity. Kinetic experiments also suggest that S37 participates in the active site/hydrogen bonding network. Nuclear magnetic resonance spectroscopy was used to determine the three-dimensional structure of the TPTP enzyme and to further examine the roles of S37 and Q67. The backbone conformation of the TPTP phosphate binding loop is nearly superimposable with that of other tyrosine phosphatases, with N14 existing in a strained, left-handed conformation that is a hallmark of the active site hydrogen bonding network in the LMW PTPs. As expected, both S37 and Q67 are located at the active site, but in the consensus structure they are not within hydrogen bonding distance of N14. The hydrogen bond interactions that are observed in X-ray structures of LMW PTPs may in fact be transient in solution. Protein dynamics within the active site hydrogen bonding network appear to be affected by the presence of substrate or bound inhibitors such as inorganic phosphate.

Abbreviations: PTP, protein tyrosine phosphatase • LMW PTP, low-molecular-weight protein tyrosine phosphatase • HMW PTP, high-molecular-weight protein tyrosine phosphatase • DS PTP, dual-specificity protein tyrosine phosphatase • BPTP, bovine protein tyrosine phosphatase • TPTP, Tritrichomonas foetus protein tyrosine phosphatase, DCl, deuterium chloride • NaOD, sodium deuteroxide • D₂O, deuterium oxide • DSS, 2,2-dimethyl-2-silapentane-5-sulfonate • k_cat, catalytic rate constant or turnover number • K_m, Michaelis-Menten constant • NMR, nuclear magnetic resonance • p-NPP, para-nitrophenyl phosphate • V_max, enzyme velocity at saturating substrate concentration

Article and publication are at http://www.proteinscience.org/cgi/doi/10.1110/ps.051618805.

Reprint requests to: Robert L. Van Etten, Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA; e-mail: vanetten{at}purdue.edu; fax: (765) 494-5274.

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

This article has been cited by other articles:

				D. Tolkatchev, R. Shaykhutdinov, P. Xu, J. Plamondon, D. C. Watson, N. M. Young, and F. Ni Three-dimensional structure and ligand interactions of the low molecular weight protein tyrosine phosphatase from Campylobacter jejuni. Protein Sci., October 1, 2006; 15(10): 2381 - 2394. [Abstract] [Full Text] [PDF]