Open AccessThe Threonine‐Sensitive Homoserine Dehydrogenase and Aspartokinase Activities of Escherichia coli K 12
Author(s) -
Janin Joël,
Cohen Georges N.
Publication year - 1969
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1969.tb00804.x
Subject(s) - threonine , allosteric regulation , chemistry , escherichia coli , biochemistry , homoserine , activator (genetics) , stereochemistry , active site , enzyme , serine , quorum sensing , virulence , gene
Aspartokinase I‐homoserine dehydrogeanase I is an allosteric protein with six subunits. Conformation changes upon addition of a substrate, l ‐aspartate, and of an activator, K + , or an inhibitor, l ‐threonine, are demonstrated by a study of the ultraviolet absorption and of the fluorescence emission of the protein. The effects of the ligands are compatible with a two‐state model and a three‐by‐three concerted transition of the subunits from the inactive, threonine binding conformation, to the active conformation binding aspartate and the potassium ions.