Mechanistic plasticity of DNA topoisomerase IB: Phosphate electrostatics dictate the need for a catalytic arginine Journal Article
| Authors: | Tian, L.; Claeboe, C. D.; Hecht, S. M.; Shuman, S. |
| Article Title: | Mechanistic plasticity of DNA topoisomerase IB: Phosphate electrostatics dictate the need for a catalytic arginine |
| Abstract: | Four conserved amino acids of type IB topoisomerases (Arg130, Lys167, Arg223, and His265 in vaccinia topoisomerase) catalyze the attack by tyrosine on the scissile phosphodiester to form a DNA-(3′-phosphotyrosyl)-enzyme intermediate. The mechanism entails general acid catalysis (by Lys167 and Arg130) and transition-state stabilization (via contact of His265 with the pro-Sp oxygen). Here we query the function of Arg223, which accelerates transesterification by a factor of 105. The requirement for Arg223 is alleviated by a neutral Sp methylphosphonate (MeP) linkage at the cleavage site. Arg223 is not required for the 30,000-fold activation of the latent endonuclease activity of topoisomerase by the Sp MeP. The rate of autohydrolysis by the DNA-(3′-MeP)-topoisomerase intermediate approaches 10% of the rate of religation to a 5′-OH DNA strand. These findings underscore the importance of transition-state electrostatics in determining the composition of the active site and dictating the balance between strand transferase and hydrolase functions. ©2005 Elsevier Ltd. All rights reserved. |
| Keywords: | nonhuman; protein function; enzyme activity; catalysis; protein folding; endonuclease; phosphate; phosphates; arginine; enzyme mechanism; transesterification; electricity; dna topoisomerase; dna topoisomerases, type i; enzyme active site; vaccinia; dna strand; transferase; hydrolase; electrostatics; methylphosphonic acid |
| Journal Title: | Structure |
| Volume: | 13 |
| Issue: | 4 |
| ISSN: | 0969-2126 |
| Publisher: | Cell Press |
| Date Published: | 2005-04-01 |
| Start Page: | 513 |
| End Page: | 520 |
| Language: | English |
| DOI: | 10.1016/j.str.2005.02.001 |
| PUBMED: | 15837190 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | --- - "Cited By (since 1996): 25" - "Export Date: 24 October 2012" - "CODEN: STRUE" - "Source: Scopus" |
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