1nla
From Proteopedia
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Solution Structure of Switch Arc, a Mutant with 3(10) Helices Replacing a Wild-Type Beta-Ribbon
Overview
Adjacent N11L and L12N mutations in the antiparallel beta-ribbon of Arc, repressor result in dramatic changes in local structure in which each, beta-strand is replaced by a right-handed helix. The full solution, structure of this "switch" Arc mutant shows that irregular 3(10) helices, compose the new secondary structure. This structural metamorphosis, conserves the number of main-chain and side-chain to main-chain hydrogen, bonds and the number of fully buried core residues. Apart from a slight, widening of the interhelical angle between alpha-helices A and B and, changes in side-chain conformation of a few core residues in Arc, no, large-scale structural adjustments in the remainder of the protein are, necessary to accommodate the ribbon-to-helix change. Nevertheless, some, changes in hydrogen-exchange rates are observed, even in regions that have, very similar structures in the two proteins. The surface of switch Arc is, packed poorly compared to wild-type, leading to approximately 1000A(2) of, additional solvent-accessible surface area, and the N termini of the 3(10), helices make unfavorable head-to-head electrostatic interactions. These, structural features account for the positive m value and salt dependence, of the ribbon-to-helix transition in Arc-N11L, a variant that can adopt, either the mutant or wild-type structures. The tertiary fold is capped in, different ways in switch and wild-type Arc, showing how stepwise, evolutionary transformations can arise through small changes in amino acid, sequence.
About this Structure
1NLA is a Single protein structure of sequence from Yersinia phage py54. Full crystallographic information is available from OCA.
Reference
Solution structure of switch Arc, a mutant with 3(10) helices replacing a wild-type beta-ribbon., Cordes MH, Walsh NP, McKnight CJ, Sauer RT, J Mol Biol. 2003 Feb 21;326(3):899-909. PMID:12581649
Page seeded by OCA on Tue Nov 20 22:21:45 2007
