title: Effects on protein structure and function of replacing tryptophan with 5-hydroxytryptophan: single-tryptophan mutants of the N-terminal domain of the bacteriophage lambda repressor.
abstract: Conformational energy computations have been carried out on the N-acetyl-N'-methylamide of 5-hydroxytryptophan (5OH-Trp) using ECEPP/3. As observed with tryptophan (Trp), the most preferred conformation about the C alpha-C beta bond of the side chain is g+ or t. This preference is reduced to only the t conformational state when 5-hydroxyTrp is in the middle of a right-handed poly(L-alanine) alpha-helix. A similar result has been obtained with Trp [Piela et al. (1987), Biopolymers 1987, 1273-1286]. These results suggest that replacement of Trp by its analog 5-hydroxyTrp may be tolerated in an alpha-helix. To test this hypothesis, we have replaced Trp by 5OH-Trp in the fifth helices of two functionally active mutants of the N-terminal domain of the bacteriophage lambda repressor. Computations on the packing of these helices have shown that no significant structural changes results from the replacement of Trp by 5OH-Trp. The DNA-binding activity of these mutants, as assessed indirectly through geometrical parameters, is also unaltered.
authors.affiliation: Department of Biochemistry, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: Kombo
authors.forename: G
authors.initials: G
authors.lastname: Némethy
authors.forename: K D
authors.initials: KD
authors.lastname: Gibson
authors.forename: J B
authors.initials: JB
authors.lastname: Ross
authors.forename: S
authors.initials: S
authors.lastname: Rackovsky
authors.forename: H A
authors.initials: HA
authors.lastname: Scheraga
mesh_terms: D006916:5-Hydroxytryptophan / Q000235:genetics / Q000378:metabolism; D000577:Amides / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D010582:Bacteriophage lambda / Q000737:chemistry*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016296:Mutagenesis / Q000235:genetics; D010455:Peptides / Q000737:chemistry; D017433:Protein Structure, Secondary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000577:Amides; D010455:Peptides; D012097:Repressor Proteins; C019529:polyalanine; C071046:N-acetyltryptophan methylamide; D014364:Tryptophan; D006916:5-Hydroxytryptophan