Escherichia coli tryptophan synthetase

Freedberg, W.B., and Hardman, J.K. (1971) Structural and functional roles of the cysteine residues in the a-subunit of the Escherichia coli tryptophan synthetase./. Biol. Chem. 246, 1439. 

Yanofsky, C., Helinski, D. and Malino, B. (1961) The effects of mutations on the composition and properties of the A protein of Escherichia coli. tryptophan synthetase. Cold Spring Harb. Symp. Quant. Biol. 26, 11-23. 

Tryptophan synthetase from Escherichia coli is a simple example of a multienzyme complex It contains two types of subunits, and /3, that have molecular weights of 29,500 and 54,000, respectively.83-84 The fully associated enzyme has the composition a2/3285 and catalyzes the reaction... 

The pyruvate dehydrogenase complex from Escherichia coli is considerably more complex than tryptophan synthetase. It has a molecular weight of approximately 4.6 millon and contains three enzymes pyruvate dehydrogenase (Et), dihydrolipoyl transacetylase (E2), and dihydrolipoyl dehydrogenase (E3).82 The overall reaction catalyzed by the complex is... 

Proteins associate with each other to form quaternary structures. Many proteins consist of more than one subunit. For example, hemoglobin has a molecular weight of 64,000 and is composed of four subunits, each of molecular weight 16,000. Two of the subunits are alike, and two are different. The enzyme tryptophan synthetase from Escherichia coli, which catalyzes the final two steps in the biosynthesis of that amino acid, consists of two nonidentical subunits, each of which catalyzes one reaction. Other enzymes contain regulatory and catalytic subunits. Still other enzymes consist of aggregates of two, three, or more identical subunits. The specific, noncovalent association of protein subunits is termed the quaternary stmcture of a protein. If the subunits are not identical, the association is called heterotypic. The association of identical subunits is termed homotypic. 

CREIGHTON, T.E., YANOFSKY, C., Association of the alpha and beta-2 subunits of the tryptophan synthetase of Escherichia coli, J. Biol. Chem., 1966,241, 980-990. 

Koyama, Y. and Furukawa, K. (1990) Qoning and sequence analysis of tryptophan synthetase genes of an extreme thermophile, Ihermus thermophilus HB27 plasmid transfer from replica-plated Escherichia coli recombinant... 

Yanoesky, C. (1959) A second reaction catalyzed by the tryptophan synthetase of Escherichia coli. Biochim. Biophys. Acta, 31,408-416. 

Crawford, 1. P. and Yanofsky, C. (1958) On the separation of the tryptophan synthetase of Escherichia coli into two protein components. Proc. Nat. Acad. Sci. 44,1161-1170. 

Yanofsky, C. and Horn, V. (1972) Tryptophan synthetase o-chain positions affected by mutations near the end of the genetic map of trpA of Escherichia coli. J. Biol. Chem. 247, 4494-4498. 

Murgola, E. j. and Yanofsky, C. (1974) Selection for new amino acids at position 211 of the tryptophan synthetase a-chain of Escherichia coli. J. Molec. Biol. 86, 775-784. 

In addition to the striking effects of sub-unit interaction upon catalytic activity and specificity which have been noted for the L-tryptophan synthetase from Escherichia coli the enzyme and its a and 2 sub-units have been shown to catalyse a variety of other reactions not entirely connected with L-tryptophan biosynthe-... 

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