+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Conformational changes in the alpha-subunit coupled to binding of the beta 2-subunit of tryptophan synthase from Escherichia coli: crystal structure of the tryptophan synthase alpha-subunit alone



Conformational changes in the alpha-subunit coupled to binding of the beta 2-subunit of tryptophan synthase from Escherichia coli: crystal structure of the tryptophan synthase alpha-subunit alone



Biochemistry 44(4): 1184-1192



When the tryptophan synthase alpha- and beta(2)-subunits combine to form the alpha(2)beta(2)-complex, the enzymatic activity of each subunit is stimulated by 1-2 orders of magnitude. To elucidate the structural basis of this mutual activation, it is necessary to determine the structures of the alpha- and beta-subunits alone and together with the alpha(2)beta(2)-complex. The crystal structures of the tryptophan synthase alpha(2)beta(2)-complex from Salmonella typhimurium (Stalpha(2)beta(2)-complex) have already been reported. However, the structures of the subunit alone from mesophiles have not yet been determined. The structure of the tryptophan synthase alpha-subunit alone from Escherichia coli (Ecalpha-subunit) was determined by an X-ray crystallographic analysis at 2.3 A, which is the first report on the subunits alone from the mesophiles. The biggest difference between the structures of the Ecalpha-subunit alone and the alpha-subunit in the Stalpha(2)beta(2)-complex (Stalpha-subunit) was as follows. Helix 2' in the Stalpha-subunit, including an active site residue (Asp60), was changed to a flexible loop in the Ecalpha-subunit alone. The conversion of the helix to a loop resulted in the collapse of the correct active site conformation. This region is also an important part for the mutual activation in the Stalpha(2)beta(2)-complex and interaction with the beta-subunit. These results suggest that the formation of helix 2'that is essential for the stimulation of the enzymatic activity of the alpha-subunit is constructed by the induced-fit mode involved in conformational changes upon interaction between the alpha- and beta-subunits. This also confirms the prediction of the conformational changes based on the thermodynamic analysis for the association between the alpha- and beta-subunits.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 048625918

Download citation: RISBibTeXText

PMID: 15667212

DOI: 10.1021/bi047927m


Related references

Conformational Changes in the a-Subunit Coupled to Binding of the b2-Subunit of Tryptophan Synthase from Escherichia coli: Crystal Structure of the Tryptophan Synthase a-Subunit Alone. Biochemistry (American Chemical Society) 44(4): 84-92, 2005

The binding of indole to the alpha-subunit and beta2-subunit and to the alpha2beta2-complex of tryptophan synthase from Escherichia coli. Identification of a second indole-binding site on the alpha-subunit. European Journal of Biochemistry 64(1): 313-320, 1976

Nicking of the tryptophan synthase beta 2-subunit at Glu-296 prevents the conformational change undergone on binding the alpha-subunit. Febs Letters 320(3): 224-228, 1993

Substrate interactions with the alpha-subunit of the Escherichia coli tryptophan synthase. A kinetic study of the wild-type alpha-subunit. Archives of Biochemistry and Biophysics 181(2): 419-427, 1977

Subunit communication in the tryptophan synthase alpha 2 beta 2 complex. Effects of beta subunit ligands on proteolytic cleavage of a flexible loop in the alpha subunit. Febs Letters 299(2): 197-200, 1992

A single amino acid switch within the hinge region of the tryptophan synthase beta subunit of Escherichia coli that leads to diminished association with alpha subunit and arrested conversion of ESII to product. Journal of Biological Chemistry 268(20): 14921-14931, 1993

Kinetics of cooperative ligand binding to the apo.beta.2 subunit of tryptophan synthase and its modulation by the .alpha. subunit. Biochemistry 19(19): 4521-4527, 1980

The alpha/beta subunit interaction in H(+)-ATPase (ATP synthase). An Escherichia coli alpha subunit mutation (Arg-alpha 296-->Cys) restores coupling efficiency to the deleterious beta subunit mutant (Ser-beta 174-->Phe). Journal of Biological Chemistry 269(14): 10265-9, 1994

Large conformational changes in the Escherichia coli tryptophan synthase beta(2) subunit upon pyridoxal 5'-phosphate binding. Febs Journal 277(9): 2157-2170, 2010

Study of cysteine residues in the alpha subunit of Escherichia coli tryptophan synthase. 1. Role in conformational stability. Protein Engineering 9(5): 425-431, 1996

Cooperative binding of alpha subunits to the Apo-beta2 subunit of tryptophan synthase from Escherichia coli. European Journal of Biochemistry 95(2): 323-326, 1979

Conformational effects of ligand binding on the beta 2 subunit of Escherichia coli tryptophan synthase analyzed with monoclonal antibodies. Biochemistry 25(9): 2502-2508, 1986

Conformational effects of ligand binding on the .beta.2 subunit of Escherichia coli tryptophan-synthase analyzed with monoclonal antibodies. Biochemistry 25(9): 2502-2508, 1986

Subunit interaction in tryptophan synthase of Escherichia coli: calorimetric studies on association of .alpha. and .beta.2 subunits. Biochemistry 18(10): 1979-1984, 1979

Subunit interaction in tryptophan synthase of Escherichia coli: calorimetric studies on association of alpha and beta 2 subunits. Biochemistry 18(10): 1979-1984, 1979