1y55
From Proteopedia
|
Crystal structure of the C122S mutant of E. Coli expressed avidin related protein 4 (AVR4)-biotin complex
Overview
The chicken avidin gene belongs to an extended gene family encoding seven, avidin-related genes (AVRs), of which only avidin is expressed in the, chicken. The sequences of AVR4 and AVR5 are identical and the common, protein (AVR4) has been expressed both in insect and bacterial systems., The recombinant proteins are similarly hyperthermostable and bind biotin, with similarly high affinities. AVR4 was crystallized in the apo and, biotin-complexed forms and their structures were determined at high, resolution. Its tertiary and quaternary structures are very similar to, those of avidin and streptavidin. Its biotin-binding site shows only a few, alterations compared with those of avidin and streptavidin, which account, for the observed differences in binding affinities. The increased, hyperthermostability can be attributed to the conformation of the critical, L3,4 loop and the extensive network of 1-3 inter-monomeric interactions., The loop contains a tandem Pro-Gly sequence and an Asp-Arg ion pair that, collectively induce rigidity, thus maintaining its closed and ordered, conformation in both the apo and biotin-complexed forms. In addition, Tyr115 is present on the AVR4 1-3 monomer-monomer interface, which is, absent in avidin and streptavidin. The interface tyrosine generates, inter-monomeric interactions, i.e. a tyrosine-tyrosine pi-pi interaction, and a hydrogen bond with Lys92. The resultant network of interactions, confers a larger 1-3 dimer-dimer contact surface on AVR4, which correlates, nicely with its higher thermostability compared with avidin and, streptavidin. Several of the proposed thermostability-determining factors, were found to play a role in strengthening the tertiary and quaternary, integrity of AVR4.
About this Structure
1Y55 is a Single protein structure of sequence from Gallus gallus with BTN and FMT as ligands. Full crystallographic information is available from OCA.
Reference
High-resolution crystal structure of an avidin-related protein: insight into high-affinity biotin binding and protein stability., Eisenberg-Domovich Y, Hytonen VP, Wilchek M, Bayer EA, Kulomaa MS, Livnah O, Acta Crystallogr D Biol Crystallogr. 2005 May;61(Pt 5):528-38. Epub 2005, Apr 20. PMID:15858262
Page seeded by OCA on Wed Nov 21 06:34:34 2007
