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Updated: Jul 28, 2026

Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses
Published on: February 25, 2011
Effects on protein structure and function of replacing tryptophan with 5-hydroxytryptophan: single-tryptophan mutants
D C Kombo1, G Némethy, K D Gibson
1Department of Biochemistry, Mount Sinai School of Medicine, New York, New York 10029, USA.
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.
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