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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. 2005 Feb 01; 44(4):1184-92.B

Abstract

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.

Authors+Show Affiliations

Nishio K
Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Morimoto Y
No affiliation info available
Ishizuka M
No affiliation info available
Ogasahara K
No affiliation info available
Tsukihara T
No affiliation info available
Yutani K
No affiliation info available

MeSH

Amino Acid SequenceCrystallizationCrystallography, X-RayEnzyme ActivationEscherichia coli ProteinsMolecular Sequence DataProtein BindingProtein ConformationProtein Structure, SecondaryProtein SubunitsSalmonella typhimuriumSequence Homology, Amino AcidThermodynamicsTryptophan Synthase

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15667212

Citation

Nishio, Kazuya, et al. "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, vol. 44, no. 4, 2005, pp. 1184-92.
Nishio K, Morimoto Y, Ishizuka M, et al. 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. 2005;44(4):1184-92.
Nishio, K., Morimoto, Y., Ishizuka, M., Ogasahara, K., Tsukihara, T., & Yutani, K. (2005). 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), 1184-92.
Nishio K, et al. 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. 2005 Feb 1;44(4):1184-92. PubMed PMID: 15667212.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - 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. AU - Nishio,Kazuya, AU - Morimoto,Yukio, AU - Ishizuka,Manabu, AU - Ogasahara,Kyoko, AU - Tsukihara,Tomitake, AU - Yutani,Katsuhide, PY - 2005/1/26/pubmed PY - 2005/3/9/medline PY - 2005/1/26/entrez SP - 1184 EP - 92 JF - Biochemistry JO - Biochemistry VL - 44 IS - 4 N2 - 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. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/15667212/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_ DB - PRIME DP - Unbound Medicine ER -