1NLA

Solution Structure of Switch Arc, a Mutant with 3(10) Helices Replacing a Wild-Type Beta-Ribbon

Summary for 1NLA

• Entry DOI: 10.2210/pdb1nla/pdb
• Related: 1QTG
• NMR Information: BMRB: 4540
• Descriptor: Transcriptional repressor arc (1 entity in total)
• Functional Keywords: 3(10) helix, beta-ribbon, beta-sheet, structural switching, transcription
• Biological source: Enterobacteria phage P22
• Total number of polymer chains: 2
• Total formula weight: 15411.65

Authors

Cordes, M.H.,Walsh, N.P.,McKnight, C.J.,Sauer, R.T. (deposition date: 2003-01-06, release date: 2003-03-18, Last modification date: 2024-05-22)

Primary citation

Cordes, M.H.,Walsh, N.P.,McKnight, C.J.,Sauer, R.T.
Solution structure of Switch Arc, a mutant with 3(10) helices replacing a wild-type beta-ribbon
J.Mol.Biol., 326:899-909, 2003

PubMed Abstract: 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.

PubMed: 12581649
DOI: 10.1016/S0022-2836(02)01425-0

Experimental method

SOLUTION NMR