2fhn
From Proteopedia
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Avidin related protein AVR4 (C122S, K109I mutant) in complex with BNA
Overview
The hydrolysis of biotinyl p-nitrophenyl ester (BNP) by a series of avidin, derivatives was examined. Surprisingly, a hyperthermostable avidin-related, protein (AVR4) was shown to display extraordinary yet puzzling hydrolytic, activity. In order to evaluate the molecular determinants that contribute, to the reaction, the crystal structure of AVR4 was compared with those of, avidin, streptavidin and key mutants of the two proteins in complex with, biotinyl p-nitroanilide (BNA), the inert amide analogue of BNP. The, structures revealed that a critical lysine residue contributes to the, hydrolysis of BNP by avidin but has only a minor contribution to the, AVR4-mediated reaction. Indeed, the respective rates of hydrolysis among, the different avidins reflect several molecular parameters, including, binding-site architecture, the availability of the ligand to solvent and, the conformation of the ligand and consequent susceptibility to efficient, nucleophilic attack. In avidin, the interaction of BNP with Lys111 and, disorder of the L3,4 loop (and consequent solvent availability) together, comprise the major driving force behind the hydrolysis, whereas in AVR4, the status of the ligand (the pseudo-substrate) is a major distinguishing, feature. In the latter protein, a unique conformation of the L3,4 loop, restrains the pseudo-substrate, thereby exposing the carbonyl carbon atom, to nucleophilic attack. In addition, due to its conformation, the, pseudo-substrate in the AVR4 complex cannot interact with the conserved, lysine analogue (Lys109); instead, this function is superseded by polar, interactions with Arg112. The results demonstrate that, in highly similar, proteins, different residues can perform the same function and that subtle, differences in the active-site architecture of such proteins can result in, alternative modes of reaction.
About this Structure
2FHN is a Single protein structure of sequence from Gallus gallus with BNI and FMT as ligands. Full crystallographic information is available from OCA.
Reference
Factors dictating the pseudocatalytic efficiency of avidins., Prizant M, Eisenberg-Domovich Y, Hytonen VP, Kulomaa MS, Wilchek M, Bayer EA, Livnah O, J Mol Biol. 2006 May 5;358(3):754-63. Epub 2006 Mar 3. PMID:16546211
Page seeded by OCA on Wed Nov 21 10:33:55 2007
Categories: Gallus gallus | Single protein | Livnah, O. | Prizant, M. | BNI | FMT | Avidin | Avr4 | High affinity | Hydrolytic activity | Streptavidin
