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- Schellman_loop abstract "Schellman Loops (also called Schellman motifs or paperclips) are commonly occurring structural features of proteins and polypeptides. Each has six amino acid residues (labelled residues i to i+5) with two specific inter-mainchain hydrogen bonds (as in lower figure, i) and a characteristic main chain dihedral angle conformation. The CO group of residue i is hydrogen-bonded to the NH of residue i+5 (colored orange in upper figure), and the CO group of residue i+1 is hydrogen-bonded to the NH of residue i+4 (beta turn, colored purple). Residues i+1, i+2, and i+3 have negative φ (phi) angle values and the phi value of residue i+4 is positive. Schellman loops incorporate a three amino acid residue RL nest (protein structural motif), in which three mainchain NH groups (from Schellman loop residues i+3 to i+5) form a concavity for hydrogen bonding to carbonyl oxygens. About 2.5% of amino acids in proteins belong to Schellman loops. Two websites are available for examining small motifs in proteins, Motivated Proteins: [1]; or PDBeMotif: [2].The majority of Schellman loops (82%) occur at the C-terminus of an alpha-helix such that residues i, i+1, i+2 and i+3 are part of the helix. Over a quarter of helices (28%) have a C-terminal Schellman loop.Occasional Schellman loops occur with seven instead of six residues. In these, the CO group of residue i is hydrogen-bonded to the NH of residue i+6, and the CO group of residue i+1 is hydrogen-bonded to the NH of residue i+5. Rare “left-handed” six-residue Schellman loops occur; these have the same hydrogen bonds, but residues i+1, i+2, and i+3 have positive φ values while the φ value of residue i+4 is negative; the nest is of the LR, rather than the RL, kind.Amino acid propensities for the six Schellman-loop residues have been described. Residue i+4 is the one most-highly conserved, with 70% of amino acids being glycine and none proline.Consideration of the hydrogen bonding in the nests of Schellman loops bound to mainchain oxygens reveals two main types of arrangement: 1,3-bridged or not. In one (lower figure, ii) the first and third nest NH groups are bridged by an oxygen atom. In the other (lower figure, iv) the first NH group is hydrogen bonded to the CO group of an amino acid four residues behind in the sequence, and none of the nest NH groups are bridged. It seems that Schellman loops are less homogeneous than might have been expected.The original Schellman criteria result in the inclusion of features not now regarded as Schellman loops. A newer set of criteria is given above.".
- Schellman_loop wikiPageExternalLink index.html.
- Schellman_loop wikiPageExternalLink pdbemotif.
- Schellman_loop wikiPageID "41978524".
- Schellman_loop wikiPageLength "9763".
- Schellman_loop wikiPageOutDegree "20".
- Schellman_loop wikiPageRevisionID "699797492".
- Schellman_loop wikiPageWikiLink Alpha_helix.
- Schellman_loop wikiPageWikiLink Amino_acid.
- Schellman_loop wikiPageWikiLink Backbone_chain.
- Schellman_loop wikiPageWikiLink Beta_turn.
- Schellman_loop wikiPageWikiLink C-terminus.
- Schellman_loop wikiPageWikiLink Carbonyl.
- Schellman_loop wikiPageWikiLink Category:Organic_chemistry.
- Schellman_loop wikiPageWikiLink Category:Protein_structural_motifs.
- Schellman_loop wikiPageWikiLink Concave_polygon.
- Schellman_loop wikiPageWikiLink Dihedral_angle.
- Schellman_loop wikiPageWikiLink File:Hydrogen_bond_arrangements_in_Schellman_loops.pdf.
- Schellman_loop wikiPageWikiLink File:Schellman_loop.pdf.
- Schellman_loop wikiPageWikiLink Glycine.
- Schellman_loop wikiPageWikiLink Hydrogen_bond.
- Schellman_loop wikiPageWikiLink Nest_(protein_structural_motif).
- Schellman_loop wikiPageWikiLink Peptide.
- Schellman_loop wikiPageWikiLink Proline.
- Schellman_loop wikiPageWikiLink Protein.
- Schellman_loop wikiPageWikiLinkText "Schellman loop".
- Schellman_loop wikiPageUsesTemplate Template:Orphan.
- Schellman_loop wikiPageUsesTemplate Template:Reflist.
- Schellman_loop subject Category:Organic_chemistry.
- Schellman_loop subject Category:Protein_structural_motifs.
- Schellman_loop comment "Schellman Loops (also called Schellman motifs or paperclips) are commonly occurring structural features of proteins and polypeptides. Each has six amino acid residues (labelled residues i to i+5) with two specific inter-mainchain hydrogen bonds (as in lower figure, i) and a characteristic main chain dihedral angle conformation.".
- Schellman_loop label "Schellman loop".
- Schellman_loop sameAs Q15845157.
- Schellman_loop sameAs m.0_r_ld2.
- Schellman_loop sameAs Q15845157.
- Schellman_loop wasDerivedFrom Schellman_loop?oldid=699797492.
- Schellman_loop isPrimaryTopicOf Schellman_loop.