2pmk

From Proteopedia

Revision as of 06:14, 13 February 2008

Crystal structures of an isolated ABC-ATPase in complex with TNP-ADP

Overview

TNP-modified nucleotides have been used extensively to study, protein-nucleotide interactions. In the case of ABC-ATPases, application, of these powerful tools has been greatly restricted due to the, significantly higher affinity of the TNP-nucleotide for the corresponding, ABC-ATPase in comparison to the non-modified nucleotides. To understand, the molecular changes occurring upon binding of the TNP-nucleotide to an, ABC-ATPase, we have determined the crystal structure of the, TNP-ADP/HlyB-NBD complex at 1.6A resolution. Despite the higher affinity, of TNP-ADP, no direct fluorophore-protein interactions were observed., Unexpectedly, only water-mediated interactions were detected between the, TNP moiety and Tyr(477), that is engaged in pi-pi stacking with the, adenine ring, as well as with two serine residues (Ser(504) and Ser(509)), of the Walker A motif. Interestingly, the side chains of these two serine, residues adopt novel conformations that are not observed in the, corresponding ADP structure. However, in the crystal structure of the, S504A mutant, which binds TNP-ADP with similar affinity to the wild type, enzyme, a novel TNP-water interaction compensates for the missing serine, side chain. Since this water molecule is not present in the wild type, enzyme, these results suggest that only water-mediated interactions, provide a structural explanation for the increased affinity of, TNP-nucleotides towards ABC-ATPases. However, our results also imply that, in silico approaches such as docking or modeling cannot directly be, applied to generate 'affinity-adopted' ADP- or ATP-analogs for, ABC-ATPases.

About this Structure

2PMK is a Single protein structure of sequence from Escherichia coli with and as ligands. Known structural/functional Sites: and . Full crystallographic information is available from OCA.

Reference

Water-mediated protein-fluorophore interactions modulate the affinity of an ABC-ATPase/TNP-ADP complex., Oswald C, Jenewein S, Smits SH, Holland IB, Schmitt L, J Struct Biol. 2007 Nov 21;. PMID:18155559

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