@article{open1828,
          volume = {83},
          number = {2},
           month = {February},
          author = {Jesmita Dhar and Pinak Chakrabarti and Harpreet Saini and G.P.S. Raghava and Raghuvansh Kishore},
            note = {Copyright of this article belongs to Wiley.},
           title = {{\ensuremath{\omega}}-Turn: a novel {\ensuremath{\beta}}-turn mimic in globular proteins stabilized by main-chain to side-chain C?H???O interaction.},
       publisher = {Wiley},
            year = {2015},
         journal = {Proteins},
           pages = {203--14},
             url = {http://crdd.osdd.net/open/1828/},
        abstract = {Mimicry of structural motifs is a common feature in proteins. The 10-membered hydrogen-bonded ring involving the main-chain C ? O in a {\ensuremath{\beta}}-turn can be formed using a side-chain carbonyl group leading to Asx-turn. We show that the N ? H component of hydrogen bond can be replaced by a C({\ensuremath{\gamma}}) -H group in the side chain, culminating in a nonconventional C ? H???O interaction. Because of its shape this {\ensuremath{\beta}}-turn mimic is designated as {\ensuremath{\omega}}-turn, which is found to occur {$\sim$} three times per 100 residues. Three residues (i to i + 2) constitute the turn with the C ? H???O interaction occurring between the terminal residues, constraining the torsion angles ?i + 1, {\ensuremath{\psi}}i + 1, ?i + 2 and {\ensuremath{\chi}}'1(i + 2) (using the interacting C({\ensuremath{\gamma}}) atom). Based on these angles there are two types of {\ensuremath{\omega}}-turns, each of which can be further divided into two groups. C({\ensuremath{\beta}}) -branched side-chains, and Met and Gln have high propensities to occur at i + 2; for the last two residues the carbonyl oxygen may participate in an additional interaction involving the S and amino group, respectively. With Cys occupying the i + 1 position, such turns are found in the metal-binding sites. N-linked glycosylation occurs at the consensus pattern Asn-Xaa-Ser/Thr; with Thr at i + 2, the sequence can adopt the secondary structure of a {\ensuremath{\omega}}-turn, which may be the recognition site for protein modification. Location between two {\ensuremath{\beta}}-strands is the most common occurrence in protein tertiary structure, and being generally exposed {\ensuremath{\omega}}-turn may constitute the antigenic determinant site. It is a stable scaffold and may be used in protein engineering and peptide design.}
}