当前位置： SCI文献检索 > BIOCHEMISTRY期刊下所有文献 > Allosteric communication in the tryptophan synthase bienzyme complex: roles of the beta-subunit aspartate 305-arginine 141 salt bridge.

Allosteric communication in the tryptophan synthase bienzyme complex: roles of the beta-subunit aspartate 305-arginine 141 salt bridge.

Abstract：

:The allosteric interactions that regulate substrate channeling and catalysis in the tryptophan synthase bienzyme complex from Salmonella typhimurium are triggered by covalent reactions at the beta-site and binding of substrate/product to the alpha-site. The transmission of these allosteric signals between the alpha- and beta-catalytic sites is modulated by an ensemble of weak bonding interactions consisting of salt bridges, hydrogen bonds, and van der Waals contacts that switch the subunits between open and closed conformations. Previous work has identified a scaffolding of salt-bridges extending between the alpha- and beta-sites consisting of alphaAsp 56, betaLys 167, and betaAsp 305. This work investigates the involvement of yet another salt bridging interaction involving the betaAsp 305-betaArg 141 pair via comparison of the spectroscopic, catalytic, and allosteric properties of the betaD305A and betaR141A mutants with the behavior of the wild-type enzyme. These mutations were found to give bienzyme complexes with impaired allosteric communication. The betaD305A mutant also exhibits altered beta-site substrate reaction specificity, while the catalytic activity of the betaR141A mutant exhibits impaired beta-site catalytic activity. The >25-fold activation of the alpha-site by alpha-aminoacrylate Schiff base formation at the beta-site found in the Na(+) form of the wild-type enzyme is abolished in the Na(+) forms of both mutants. Replacing Na(+) by NH(4)(+) or Cs(+) restores the betaD305A to a wild-type-like behavior, whereas only partial restoration is achieved with the betaR141A mutant. These studies establish that the betaD305-betaR141 salt bridge plays a crucial role both in the formation of the closed conformation of the beta-site and in the transmission of allosteric signals between the alpha- and beta-sites that switch the alpha-site on and off.

journal_name

Biochemistry

journal_title

Biochemistry

authors

Ferrari D,Niks D,Yang LH,Miles EW,Dunn MF

doi

10.1021/bi034291a

subject

Has Abstract

pub_date

2003-07-01 00:00:00

pages

7807-18

issue

eissn

0006-2960

issn

1520-4995

journal_volume

pub_type

杂志文章

在线工具

Allosteric communication in the tryptophan synthase bienzyme complex: roles of the beta-subunit aspartate 305-arginine 141 salt bridge.