Exploring weak, transient protein-protein interactions in crowded in vivo environments by in-cell NMR spectroscopy.
 

Exploring weak, transient protein-protein interactions in crowded in vivo environments by in-cell NMR spectroscopy.

Exploring weak, transient protein-protein interactions in crowded in vivo environments by in-cell NMR spectroscopy.

Biochemistry. 2011 Sep 26;

Authors: Wang Q, Zhuravleva A, Gierasch LM

Abstract
Biology relies on functional interplay of proteins in the crowded and heterogeneous environment inside cells, and functional protein interactions are often weak and transient. Thus, methods are needed that preserve these interactions and provide information about them. In-cell NMR spectroscopy is an attractive method to study a protein's behavior in cells because it may provide residue-level structural and dynamic information. Yet several factors limit the feasibility of protein NMR spectroscopy in cells, and among them slow rotational diffusion has emerged as the most important. In this paper, we seek to elucidate the causes of the dramatically slow protein tumbling in cells and in so doing to gain insight into how the intracellular viscosity and weak, transient interactions modulate protein mobility. To address these questions, we characterized the rotational diffusion of three model globular proteins in E. coli cells using 2D heteronuclear NMR spectroscopy. These proteins have a similar molecular size and globular fold, but very different surface properties, and indeed, they show very different rotational diffusion in the E. coli intracellular environment. Our data are consistent with an intracellular viscosity approximately eight times that of water-too low to be a limiting factor to observing small globular proteins by in-cell NMR spectroscopy. Thus, we conclude that transient interactions with cytoplasmic components significantly and differentially affect the mobility of proteins and therefore their NMR detectability. Moreover, we suggest that an intricate interplay of total protein charge and hydrophobic interactions plays a key role in regulating these weak intermolecular interactions in cells.


PMID: 21942871 [PubMed - as supplied by publisher]



Source: PubMed