pH driven conformational dynamics and dimer‐to‐monomer transition in DLC8

• Published in: Protein science Vol. 15; no. 2; pp. 335 - 342
• Main Authors: Mohan, P.M. Krishna, Barve, Maneesha, Chatterjee, Amarnath, Hosur, Ramakrishna V.
• Format: Journal Article
• Language: English
• Published: Bristol Cold Spring Harbor Laboratory Press 01.02.2006
• Subjects: 15N transverse relaxation; Animals; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; conformational exchange; Dimerization; dimer–monomer equilibrium; DLC8, dynein light chain protein; Drosophila melanogaster - metabolism; Drosophila Proteins - chemistry; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; dynein light chain protein; Dyneins - chemistry; Dyneins - genetics; Dyneins - metabolism; HSQC, hetero‐nuclear single quantum coherence; Hydrogen-Ion Concentration; line broadening; Magnetic Resonance Spectroscopy; NMR, nuclear magnetic resonance; nuclear magnetic resonance; pH driven conformational transitions; Protein Binding; Protein Conformation; Protons
• ISSN: 0961-8368; 1469-896X
• DOI: 10.1110/ps.051854906

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.