Stranded in isolation: structural role of isolated extended strands in proteins

Eswar, Narayanan ; Ramakrishnan, C. ; Srinivasan, N. (2003) Stranded in isolation: structural role of isolated extended strands in proteins Protein Engineering, 16 (5). pp. 331-339. ISSN 0269-2139

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Reasons for the formation of extended-strands (E-strands) in proteins are often associated with the formation of β -sheets. However E-strands, not part of β-sheets, commonly occur in proteins. This raises questions about the structural role and stability of such isolated E-strands. Using a dataset of 250 largely non-homologous and high-resolution (<2 Å) crystal structures of proteins, we have identified 518 isolated E-strands from 187 proteins. The two most distinguishing features of isolated E-strands from β-strands in β-sheets are the high preponderance of prolyl residues occuring in isolated E-strands and their high exposure to the surroundings. Removal of regions with polyproline conformation from the dataset did not significantly reduce the propensity of prolyl residues to occur in isolated E-strands. Isolated E-strands are often characterized by their main-chain amide and carbonyl groups involved in hydrogen bonding with polar side chains or water. They are often flanked by irregular loop structures and are less well conserved, than β-sheet forming β-strands, among homologous protein structures. It is suggested that isolated β-strands have many characteristics of loop segments but with repetitive (φ,ψ) values falling within the β-region of the Ramachandran map.

Item Type:Article
Source:Copyright of this article belongs to Oxford University Press.
Keywords:β-sheet; β-strand; Extended Strand; Hydrogen Bonding; Protein Structures
ID Code:41024
Deposited On:26 May 2011 06:49
Last Modified:17 May 2016 22:53

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