Importance of residues 2-9 in the immunoreactivity, subunit interactions, and activity of the beta 2 subunit of Escherichia coli tryptophan synthase

The epitope recognized by a monoclonal antibody (mAb19) directed against the beta 2 subunit of Escherichia coli tryptophan synthase was found to be carried by residues 2-9 of the beta chain. The affinities of mAb19 for peptides of different lengths containing the 2-9 sequence were close to 0.6 x 10(...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of biological chemistry 1995-03, Vol.270 (9), p.4255-4261
Main Authors: Navon, A, Schulze, A J, Guillou, Y, Zylinski, C A, Baleux, F, Expert-Bezançon, N, Friguet, B, Djavadi-Ohaniance, L, Goldberg, M E
Format: Article
Language:English
Subjects:
Antibodies, Monoclonal - immunology
Circular Dichroism
Codon
Enzyme Stability
Epitopes - immunology
Escherichia coli - enzymology
Peptide Fragments - chemical synthesis
Peptide Fragments - immunology
Peptide Fragments - metabolism
Protein Folding
Spectrophotometry, Ultraviolet
Tryptophan Synthase - genetics
Tryptophan Synthase - immunology
Tryptophan Synthase - isolation & purification
Tryptophan Synthase - metabolism
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The epitope recognized by a monoclonal antibody (mAb19) directed against the beta 2 subunit of Escherichia coli tryptophan synthase was found to be carried by residues 2-9 of the beta chain. The affinities of mAb19 for peptides of different lengths containing the 2-9 sequence were close to 0.6 x 10(9) M-1, the affinity of mAb19 for native beta 2. In view of these results, a model is proposed to account for the kinetics of appearance of the epitope during in vitro renaturation of beta 2 (Murry-Brelier, A., and Goldberg, M.E. (1988) Biochemistry 27, 7633-7640). A mutant producing beta chains lacking residues 1-9 (beta delta 1-9) was prepared. The beta delta 1-9 protein was able to fold into a heat stable homodimer resembling wild type beta 2. Isolated beta delta 1-9 had no detectable enzymatic activity. It could bind alpha chains extremely weakly and be slightly activated. In the presence of the 1-9 peptide, the beta delta 1-9 protein could bind alpha chains much more strongly and generate a 50% active enzyme. Thus, although having little role in the overall folding and stability of the protein, the 1-9 sequence of the beta chain appears strongly involved in the alpha-beta interactions and in the enzymatic activity.
ISSN:0021-9258