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Published online before print December 29, 2005, 10.1110/ps.051854906
Protein Science (2006), 15:335-342. Published by Cold Spring Harbor Laboratory Press. Copyright © 2006 The Protein Society
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pH driven conformational dynamics and dimer-to-monomer transition in DLC8

P.M. Krishna Mohan, Maneesha Barve, Amarnath Chatterjee and Ramakrishna V. Hosur

Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400 005, India

(RECEIVED September 27, 2005; FINAL REVISION November 2, 2005; ACCEPTED November 8, 2005)

Dynein light chain protein, a part of the cytoplasmic motor assembly, is a homodimer at physiological pH and dissociates below pH 4.5 to a monomer. The dimer binds to a variety of cargo, whereas the monomer does not bind any of the target proteins. We report here the pH induced stepwise structural and motional changes in the protein, as derived from line broadening and 15N transverse relaxation measurements. At pH 7 and below until 5, partial protonation and consequent interconversion between molecules carrying protonated and neutral histidines, causes conformational dynamics in the dimeric protein and this increases with decreasing pH. Enhanced dynamics in turn leads to partial loosening of the structure. This would have implications for different efficacies of binding by target proteins due to small variations in pH in different parts of the cell, and hence for cargo trafficking from one part to another. Below pH 5, enhanced charge repulsions, partial loss of hydrophobic interactions, and destabilization of H-bonds across the dimer interface cause further loosening of the dimeric structure, leading eventually to the dissociation of the dimer.

Keywords: dynein light chain protein; 15N transverse relaxation; conformational exchange; line broadening; pH driven conformational transitions; nuclear magnetic resonance; dimer–monomer equilibrium

Abbreviations: NMR, nuclear magnetic resonance • HSQC, hetero-nuclear single quantum coherence • DLC8, dynein light chain protein

Article published online ahead of print. Article and publication date are at http://www.proteinscience.org/cgi/doi/10.1110/ps.051854906.

Reprint requests to: Professor Ramakrishna V. Hosur, Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India; e-mail: hosur{at}tifr.res.in; fax: 91-22-2280-4610.


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