Sequence and conformational preferences at termini of alpha-helices in membrane proteins: Role of the helix environment

Shelar, Ashish and Bansal, Manju (2014) Sequence and conformational preferences at termini of alpha-helices in membrane proteins: Role of the helix environment. In: PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS, 82 (12). pp. 3420-3436.

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Abstract

-helices are amongst the most common secondary structural elements seen in membrane proteins and are packed in the form of helix bundles. These -helices encounter varying external environments (hydrophobic, hydrophilic) that may influence the sequence preferences at their N and C-termini. The role of the external environment in stabilization of the helix termini in membrane proteins is still unknown. Here we analyze -helices in a high-resolution dataset of integral -helical membrane proteins and establish that their sequence and conformational preferences differ from those in globular proteins. We specifically examine these preferences at the N and C-termini in helices initiating/terminating inside the membrane core as well as in linkers connecting these transmembrane helices. We find that the sequence preferences and structural motifs at capping (Ncap and Ccap) and near-helical (N' and C') positions are influenced by a combination of features including the membrane environment and the innate helix initiation and termination property of residues forming structural motifs. We also find that a large number of helix termini which do not form any particular capping motif are stabilized by formation of hydrogen bonds and hydrophobic interactions contributed from the neighboring helices in the membrane protein. We further validate the sequence preferences obtained from our analysis with data from an ultradeep sequencing study that identifies evolutionarily conserved amino acids in the rat neurotensin receptor. The results from our analysis provide insights for the secondary structure prediction, modeling and design of membrane proteins. Proteins 2014; 82:3420-3436. (c) 2014 Wiley Periodicals, Inc.

Item Type:	Journal Article
Publication:	PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS
Publisher:	WILEY-BLACKWELL
Additional Information:	Copyright for this article belongs to the WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Keywords:	membrane protein folding; membrane protein modeling; protein design; structural biology; helix termini; helix capping
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	26 Dec 2014 06:46
Last Modified:	26 Dec 2014 06:46
URI:	http://eprints.iisc.ac.in/id/eprint/50514

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