Dissecting pi-helices: sequence, structure and function

Kumar, Prasun and Bansal, Manju (2015) Dissecting pi-helices: sequence, structure and function. In: FEBS JOURNAL, 282 (22). pp. 4415-4432.

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Abstract

A new procedure for the identification of regular secondary structures using a C-alpha trace has identified 659 pi-helices in 3582 protein chains, solved at high resolution. Taking advantage of this significantly expanded database of pi-helices, we have analysed the functional and structural roles of helices and determined the position-wise amino acid propensity within and around them. These helices range from 5 to 18 residues in length with the average twist and rise being 85.2 +/- 7.2 and 1.28 +/- 0.31 angstrom, respectively. A total of 546 (similar to 83%) out of 659 pi-helices occur in conjunction with alpha-helices, with 101 pi-helices being interspersed between two alpha-helices. The majority of interspersed pi-helices were found to be conserved across a large number of structures within a protein family and produce a significant bend in the overall helical segment as well as local distortions in the neighbouring a-helices. The presence of a pi-helical fragment leads to appropriate orientation of the constituent residues, so as to facilitate favourable interactions and also help in proper folding of the protein chain. In addition to intra helical 6 -> 1 N H center dot center dot center dot O hydrogen bonds, pi-helices are also stabilized by several other non-bonded interactions. pi-Helices show distinct positional residue preferences, which are different from those of a-helices.

Item Type:	Journal Article
Publication:	FEBS JOURNAL
Publisher:	WILEY-BLACKWELL
Additional Information:	Copy right for this article belongs to the WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Keywords:	amino acid propensity; ASSP; interspersed; pi-helices; secondary structures; pi/alpha interface
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	10 Feb 2016 06:11
Last Modified:	10 Feb 2016 06:11
URI:	http://eprints.iisc.ac.in/id/eprint/53215

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