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Water‐mediated contacts in the trp ‐repressor operator complex recognition process

Water‐mediated contacts in the trp ‐repressor operator complex recognition process Water‐mediated contacts are known as an important recognition tool in trp‐repressor operator systems. One of these contacts involves two conserved base pairs (G6 · C−6 and A5 · T−5) and three amino acids (Lys 72, Ile 79, and Ala 80). To investigate the nature of these contacts, we analyzed the X‐ray structure (PDB code: 1TRO) of the trp‐repressor operator complex by means of molecular dynamics simulations. This X‐ray structure contains two dimers that exhibit structural differences. From these two different starting structures, two 10 ns molecular dynamics simulations have been performed. Both of our simulations show an increase of water molecules in the major groove at one side of the dimer, while the other side remains unchanged compared to the X‐ray structure. Though the maximum residence time of the concerned water molecules decreases with an increase of solvent at the interface, these water molecules continue to play an important role in mediating DNA–protein contacts. This is shown by new stable amino acids–DNA distances and a long water residence time compared to free DNA simulation. To maintain stability of the new contacts, the preferential water binding site on O6(G6) is extended. This extension agrees with mutation experiment data on A5 and G6, which shows different relative affinity due to mutation on these bases (A. Joachimiak, T. E. Haran, P. B. Sigler, EMBO Journal 1994, Vol. 13, No. (2) pp. 367–372). Due to the rearrangements in the system, the phosphate of the base G6 is able to interconvert to the BII substate, which is not observed on the other half side of the complex. The decrease of the number of hydrogen bonds between protein and DNA backbone could be the initial step of the dissociation process of the complex, or in other words an intermediate complex conformation of the association process. Thus, we surmise that these features show the importance of water‐mediated contacts in the trp‐repressor operator recognition process. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biopolymers Wiley

Water‐mediated contacts in the trp ‐repressor operator complex recognition process

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References (56)

Publisher
Wiley
Copyright
Copyright © 2004 Wiley Periodicals, Inc., A Wiley Company
ISSN
0006-3525
eISSN
1097-0282
DOI
10.1002/bip.20023
pmid
15048770
Publisher site
See Article on Publisher Site

Abstract

Water‐mediated contacts are known as an important recognition tool in trp‐repressor operator systems. One of these contacts involves two conserved base pairs (G6 · C−6 and A5 · T−5) and three amino acids (Lys 72, Ile 79, and Ala 80). To investigate the nature of these contacts, we analyzed the X‐ray structure (PDB code: 1TRO) of the trp‐repressor operator complex by means of molecular dynamics simulations. This X‐ray structure contains two dimers that exhibit structural differences. From these two different starting structures, two 10 ns molecular dynamics simulations have been performed. Both of our simulations show an increase of water molecules in the major groove at one side of the dimer, while the other side remains unchanged compared to the X‐ray structure. Though the maximum residence time of the concerned water molecules decreases with an increase of solvent at the interface, these water molecules continue to play an important role in mediating DNA–protein contacts. This is shown by new stable amino acids–DNA distances and a long water residence time compared to free DNA simulation. To maintain stability of the new contacts, the preferential water binding site on O6(G6) is extended. This extension agrees with mutation experiment data on A5 and G6, which shows different relative affinity due to mutation on these bases (A. Joachimiak, T. E. Haran, P. B. Sigler, EMBO Journal 1994, Vol. 13, No. (2) pp. 367–372). Due to the rearrangements in the system, the phosphate of the base G6 is able to interconvert to the BII substate, which is not observed on the other half side of the complex. The decrease of the number of hydrogen bonds between protein and DNA backbone could be the initial step of the dissociation process of the complex, or in other words an intermediate complex conformation of the association process. Thus, we surmise that these features show the importance of water‐mediated contacts in the trp‐repressor operator recognition process. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004

Journal

BiopolymersWiley

Published: Apr 15, 2004

Keywords: water‐mediated contacts; trp‐repressor operator; x‐ray structure; molecular dynamics; DNA–protein contacts; amino acids–DNA distances; water residence time

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