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Termination of right handed helices in proteins by residues in left handed helical conformations
Author(s) -
Nagarajaram H.A.,
Sowdhamini R.,
Ramakrishnan C.,
Balaram P.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80625-5
Subject(s) - residue (chemistry) , helix (gastropod) , chemistry , hydrogen bond , crystallography , left handed , stereochemistry , right handed , amino acid residue , protein structure , alpha helix , circular dichroism , peptide sequence , molecule , biochemistry , biology , physics , ecology , organic chemistry , neutrino , snail , gene , nuclear physics , optics
An analysis of 636 helical segments, ranging in length from 4 to 32 residues, from 123 independent protein crystal structures reveals that helix termination by residues in left handed (α L ) helical conformations is a common occurrence. Gly and Asn residues are the most frequent α L helix terminators, with the former having a very high propensity to adopt such conformations. The α R ‐α R ‐α R ‐α L segment at the C termini of protein helices often possesses a 6 → 1 (π‐type) hydrogen bond between the CO of residue i and the NH of residue i + 5 with residue i + 4 occurring in the α L conformation. A stereochemical analysis of 216 examples shows that in 62 cases the 6 → 1 hydrogen bond is absent. The present analysis provides a quantitative measure of the propensity of the 20 amino acids to adopt α L helix terminating conformations.